Q1. What is the difference
between an Abstract class and Interface?
1. Abstract classes may have some executable methods and methods left
unimplemented. Interfaces contain no implementation code.
2. An class can implement any number of interfaces, but subclass at most one abstract class.
3. An abstract class can have nonabstract methods. All methods of an interface are abstract.
4. An abstract class can have instance variables. An interface cannot.
5. An abstract class can define constructor. An interface cannot.
6. An abstract class can have any visibility: public, protected, private or none
(package). An interface's visibility must be public or none (package).
7. An abstract class inherits from Object and includes methods such as clone() andequals().
1. Abstract classes may have some executable methods and methods left
unimplemented. Interfaces contain no implementation code.
2. An class can implement any number of interfaces, but subclass at most one abstract class.
3. An abstract class can have nonabstract methods. All methods of an interface are abstract.
4. An abstract class can have instance variables. An interface cannot.
5. An abstract class can define constructor. An interface cannot.
6. An abstract class can have any visibility: public, protected, private or none
(package). An interface's visibility must be public or none (package).
7. An abstract class inherits from Object and includes methods such as clone() andequals().
Q2.What are checked and unchecked
exceptions?
Java defines two kinds of exceptions :
• Checked exceptions : Exceptions that inherit from the Exception class are
checked exceptions. Client code has to handle the checked exceptions thrown by
the API, either in a catch clause or by forwarding it outward with the throws clause.
Examples - SQLException, IOxception.
• Unchecked exceptions : RuntimeException also extends from Exception. However,
all of the exceptions that inherit from RuntimeException get special treatment.
There is no requirement for the client code to deal with them, and hence they are
called unchecked exceptions. Example Unchecked exceptions are
NullPointerException, OutOfMemoryError, DivideByZeroException typically,
programming errors.
Java defines two kinds of exceptions :
• Checked exceptions : Exceptions that inherit from the Exception class are
checked exceptions. Client code has to handle the checked exceptions thrown by
the API, either in a catch clause or by forwarding it outward with the throws clause.
Examples - SQLException, IOxception.
• Unchecked exceptions : RuntimeException also extends from Exception. However,
all of the exceptions that inherit from RuntimeException get special treatment.
There is no requirement for the client code to deal with them, and hence they are
called unchecked exceptions. Example Unchecked exceptions are
NullPointerException, OutOfMemoryError, DivideByZeroException typically,
programming errors.
Q3.What is a user defined exception?
User-defined exceptions may be implemented by
• defining a class to respond to the exception and
• embedding a throw statement in the try block where the exception can occur or
declaring that the method throws the exception (to another method where it is handled).
The developer can define a new exception by deriving it from the Exception class as follows:
public class MyException extends Exception {
/* class definition of constructors (but NOT the exception handling code) goes here public MyException() {
super();
}
public MyException( String errorMessage ) {
super( errorMessage );
}
}
The throw statement is used to signal the occurance of the exception within a try block. Often, exceptions are instantiated in the same statement in which they are thrown using the syntax.
throw new MyException("I threw my own exception.")
To handle the exception within the method where it is thrown, a catch statement that handles MyException, must follow the try block. If the developer does not want to handle the exception in the method itself, the method must pass the exception using the syntax:
public myMethodName() throws MyException
User-defined exceptions may be implemented by
• defining a class to respond to the exception and
• embedding a throw statement in the try block where the exception can occur or
declaring that the method throws the exception (to another method where it is handled).
The developer can define a new exception by deriving it from the Exception class as follows:
public class MyException extends Exception {
/* class definition of constructors (but NOT the exception handling code) goes here public MyException() {
super();
}
public MyException( String errorMessage ) {
super( errorMessage );
}
}
The throw statement is used to signal the occurance of the exception within a try block. Often, exceptions are instantiated in the same statement in which they are thrown using the syntax.
throw new MyException("I threw my own exception.")
To handle the exception within the method where it is thrown, a catch statement that handles MyException, must follow the try block. If the developer does not want to handle the exception in the method itself, the method must pass the exception using the syntax:
public myMethodName() throws MyException
Q4.What is the difference between C++
& Java?
Well as Bjarne Stroustrup says "..despite the syntactic similarities, C++ and Java are very different languages. In many ways, Java seems closer to Smalltalk than to C++..". Here are few I discovered:
• Java is multithreaded
• Java has no pointers
• Java has automatic memory management (garbage collection)
• Java is platform independent (Stroustrup may differ by saying "Java is a platform"
• Java has built-in support for comment documentation
• Java has no operator overloading
• Java doesn’t provide multiple inheritance
• There are no destructors in Java
Well as Bjarne Stroustrup says "..despite the syntactic similarities, C++ and Java are very different languages. In many ways, Java seems closer to Smalltalk than to C++..". Here are few I discovered:
• Java is multithreaded
• Java has no pointers
• Java has automatic memory management (garbage collection)
• Java is platform independent (Stroustrup may differ by saying "Java is a platform"
• Java has built-in support for comment documentation
• Java has no operator overloading
• Java doesn’t provide multiple inheritance
• There are no destructors in Java
Q5.What are statements in JAVA
?
Statements are equivalent to sentences in natural languages. A statement forms a complete
unit of execution. The following types of expressions can be made into a statement by
terminating the expression with a semicolon
• Assignment expressions
• Any use of ++ or --
• Method calls
• Object creation expressions
These kinds of statements are called expression statements. In addition to these kinds of
expression statements, there are two other kinds of statements. A declaration statement
declares a variable. A control flow statement regulates the order in which statements get
executed. The for loop and the if statement are both examples of control flow statements.
Statements are equivalent to sentences in natural languages. A statement forms a complete
unit of execution. The following types of expressions can be made into a statement by
terminating the expression with a semicolon
• Assignment expressions
• Any use of ++ or --
• Method calls
• Object creation expressions
These kinds of statements are called expression statements. In addition to these kinds of
expression statements, there are two other kinds of statements. A declaration statement
declares a variable. A control flow statement regulates the order in which statements get
executed. The for loop and the if statement are both examples of control flow statements.
Q6.What is JAR file?
JavaARchive files are a big glob of Java classes, images, audio, etc., compressed to make
one simple, smaller file to ease Applet downloading. Normally when a browser encounters
an applet, it goes and downloads all the files, images, audio, used by the Applet separately.
This can lead to slower downloads.
JavaARchive files are a big glob of Java classes, images, audio, etc., compressed to make
one simple, smaller file to ease Applet downloading. Normally when a browser encounters
an applet, it goes and downloads all the files, images, audio, used by the Applet separately.
This can lead to slower downloads.
Q7.What is JNI?
JNI is an acronym of Java Native Interface. Using JNI we can call functions which are written in other languages from Java. Following are its advantages and disadvantages.
Advantages:
• You want to use your existing library which was previously written in other language.
• You want to call Windows API function.
• For the sake of execution speed.
• You want to call API function of some server product which is in c or c++ from java client.
Disadvantages:
• You can’t say write once run anywhere.
• Difficult to debug runtime error in native code.
• Potential security risk.
• You can’t call it from Applet.
JNI is an acronym of Java Native Interface. Using JNI we can call functions which are written in other languages from Java. Following are its advantages and disadvantages.
Advantages:
• You want to use your existing library which was previously written in other language.
• You want to call Windows API function.
• For the sake of execution speed.
• You want to call API function of some server product which is in c or c++ from java client.
Disadvantages:
• You can’t say write once run anywhere.
• Difficult to debug runtime error in native code.
• Potential security risk.
• You can’t call it from Applet.
Q8.What is serialization?
Quite simply, object serialization provides a program the ability to read or write a whole object to and from a raw byte stream. It allows Java objects and primitives to be encoded into a byte stream suitable for streaming to some type of network or to a file-system, or more generally, to a transmission medium or storage facility. A seralizable object must implement the Serilizable interface. We use ObjectOutputStream to write this object to a stream and ObjectInputStream to read it from the stream.
Quite simply, object serialization provides a program the ability to read or write a whole object to and from a raw byte stream. It allows Java objects and primitives to be encoded into a byte stream suitable for streaming to some type of network or to a file-system, or more generally, to a transmission medium or storage facility. A seralizable object must implement the Serilizable interface. We use ObjectOutputStream to write this object to a stream and ObjectInputStream to read it from the stream.
Q9.Why there are some null
interface in java ? What does it mean ? Give me some null
interfaces in JAVA?
Null interfaces act as markers..they just tell the compiler that the objects of this class need to be treated differently..some marker interfaces are : Serializable, Remote, Cloneable
Null interfaces act as markers..they just tell the compiler that the objects of this class need to be treated differently..some marker interfaces are : Serializable, Remote, Cloneable
Q10. Is synchronised a modifier?indentifier??what
is it??
It's a modifier. Synchronized methods are methods that are used to control access to an object. A thread only executes a synchronized method after it has acquired the lock for the method's object or class. Synchronized statements are similar to synchronized methods. A synchronized statement can only be executed after a thread has acquired the lock for the object or class referenced in the synchronized statement.
It's a modifier. Synchronized methods are methods that are used to control access to an object. A thread only executes a synchronized method after it has acquired the lock for the method's object or class. Synchronized statements are similar to synchronized methods. A synchronized statement can only be executed after a thread has acquired the lock for the object or class referenced in the synchronized statement.
Q11.What is singleton class?where is it
used?
Singleton is a design pattern meant to provide one and only one instance of an object. Other objects can get a reference to this instance through a static method (class constructor is kept private). Why do we need one? Sometimes it is necessary, and often sufficient, to create a single instance of a given class. This has advantages in memory management, and for Java, in garbage collection. Moreover, restricting the number of instances may be necessary or desirable for technological or business reasons--for example, we may only want a single instance of a pool of database connections.
Singleton is a design pattern meant to provide one and only one instance of an object. Other objects can get a reference to this instance through a static method (class constructor is kept private). Why do we need one? Sometimes it is necessary, and often sufficient, to create a single instance of a given class. This has advantages in memory management, and for Java, in garbage collection. Moreover, restricting the number of instances may be necessary or desirable for technological or business reasons--for example, we may only want a single instance of a pool of database connections.
Q12.What is a compilation unit?
The smallest unit of source code that can be compiled, i.e. a .java file.
The smallest unit of source code that can be compiled, i.e. a .java file.
Q13.Is string a wrapper class?
String is a class, but not a wrapper class. Wrapper classes like (Integer) exist for each primitive type. They can be used to convert a primitive data value into an object, and viceversa.
String is a class, but not a wrapper class. Wrapper classes like (Integer) exist for each primitive type. They can be used to convert a primitive data value into an object, and viceversa.
Q14.Why java does not have multiple
inheritance?
The Java design team strove to make Java:
• Simple, object oriented, and familiar
• Robust and secure
• Architecture neutral and portable
• High performance
• Interpreted, threaded, and dynamic
The reasons for omitting multiple inheritance from the Java language mostly stem from the "simple, object oriented, and familiar" goal. As a simple language, Java's creators wanted a language that most developers could grasp without extensive training. To that end, they worked to make the language as similar to C++ as possible (familiar) without carrying over C++'s unnecessary complexity (simple).
In the designers' opinion, multiple inheritance causes more problems and confusion than it solves. So they cut multiple inheritance from the language (just as they cut operator overloading). The designers' extensive C++ experience taught them that multiple inheritance just wasn't worth the headache.
The Java design team strove to make Java:
• Simple, object oriented, and familiar
• Robust and secure
• Architecture neutral and portable
• High performance
• Interpreted, threaded, and dynamic
The reasons for omitting multiple inheritance from the Java language mostly stem from the "simple, object oriented, and familiar" goal. As a simple language, Java's creators wanted a language that most developers could grasp without extensive training. To that end, they worked to make the language as similar to C++ as possible (familiar) without carrying over C++'s unnecessary complexity (simple).
In the designers' opinion, multiple inheritance causes more problems and confusion than it solves. So they cut multiple inheritance from the language (just as they cut operator overloading). The designers' extensive C++ experience taught them that multiple inheritance just wasn't worth the headache.
Q15.Why java is not a 100% oops?
Many people say this because Java uses primitive types such as int, char, double. But then all the rest are objects. Confusing question.
Many people say this because Java uses primitive types such as int, char, double. But then all the rest are objects. Confusing question.
Q16.What is a resource bundle?
In its simplest form, a resource bundle is represented by a text file containing keys and a text value for each key.
In its simplest form, a resource bundle is represented by a text file containing keys and a text value for each key.
Q17.What is transient
variable?
Transient variable can't be serialize. For example if a variable is declared as transient in a Serializable class and the class is written to an ObjectStream, the value of the variable can't be written to the stream instead when the class is retrieved from the ObjectStream the value of the variable becomes null.
Transient variable can't be serialize. For example if a variable is declared as transient in a Serializable class and the class is written to an ObjectStream, the value of the variable can't be written to the stream instead when the class is retrieved from the ObjectStream the value of the variable becomes null.
Q18.What is Collection API?
The Collection API is a set of classes and interfaces that support operation on collections of objects. These classes and interfaces are more flexible, more powerful, and more regular than the vectors, arrays, and hashtables if effectively replaces.
Example of classes: HashSet, HashMap, ArrayList, LinkedList, TreeSet and TreeMap.
Example of interfaces: Collection, Set, List and Map.
The Collection API is a set of classes and interfaces that support operation on collections of objects. These classes and interfaces are more flexible, more powerful, and more regular than the vectors, arrays, and hashtables if effectively replaces.
Example of classes: HashSet, HashMap, ArrayList, LinkedList, TreeSet and TreeMap.
Example of interfaces: Collection, Set, List and Map.
Q19.Is Iterator a Class or Interface? What
is its use?
Iterator is an interface which is used to step through the elements of a Collection.
Iterator is an interface which is used to step through the elements of a Collection.
Q20.What is similarities/difference
between an Abstract class
and Interface?
Differences are as follows:
• Interfaces provide a form of multiple inheritance. A class can extend only one other class.
• Interfaces are limited to public methods and constants with no implementation.
Abstract classes can have a partial implementation, protected parts, static methods, etc.
• A Class may implement several interfaces. But in case of abstract class, a class may extend only one abstract class.
• Interfaces are slow as it requires extra indirection to to find corresponding method in in the actual class. Abstract classes are fast.
Similarities:
• Neither Abstract classes or Interface can be instantiated.
Differences are as follows:
• Interfaces provide a form of multiple inheritance. A class can extend only one other class.
• Interfaces are limited to public methods and constants with no implementation.
Abstract classes can have a partial implementation, protected parts, static methods, etc.
• A Class may implement several interfaces. But in case of abstract class, a class may extend only one abstract class.
• Interfaces are slow as it requires extra indirection to to find corresponding method in in the actual class. Abstract classes are fast.
Similarities:
• Neither Abstract classes or Interface can be instantiated.
Q21.What is a transient
variable?
A transient variable is a variable that may not be serialized.
A transient variable is a variable that may not be serialized.
Q22.Which containers use a border Layout
as their default layout?
The window, Frame and Dialog classes use a border layout as their default layout.
The window, Frame and Dialog classes use a border layout as their default layout.
Q23.Why do threads block on I/O?
Threads block on i/o (that is enters the waiting state) so that other threads may execute while the i/o Operation is performed.
Threads block on i/o (that is enters the waiting state) so that other threads may execute while the i/o Operation is performed.
Q24.How are Observer and Observable used?
Objects that subclass the Observable class maintain a list of observers. When an Observable object is updated it invokes the update() method of each of its observers to notify the observers that it has changed state. The Observer interface is implemented by objects that observe Observable objects.
Objects that subclass the Observable class maintain a list of observers. When an Observable object is updated it invokes the update() method of each of its observers to notify the observers that it has changed state. The Observer interface is implemented by objects that observe Observable objects.
Q25.What is synchronization
and why is it important?
With respect to multithreading, synchronization is the capability to control the access of multiple threads to shared resources. Without synchronization, it is possible for one thread to modify a shared object while another thread is in the process of using or updating that object's value. This often leads to significant errors.
With respect to multithreading, synchronization is the capability to control the access of multiple threads to shared resources. Without synchronization, it is possible for one thread to modify a shared object while another thread is in the process of using or updating that object's value. This often leads to significant errors.
Q26. Can a lock be acquired on a class?
Yes, a lock can be acquired on a class. This lock is acquired on the class's Class object.
Yes, a lock can be acquired on a class. This lock is acquired on the class's Class object.
Q27. What's new with the stop(), suspend()
and resume() methods
in JDK 1.2?
The stop(), suspend() and resume() methods have been deprecated in JDK 1.2.
The stop(), suspend() and resume() methods have been deprecated in JDK 1.2.
Q28. Is null a keyword?
The null value is not a keyword.
The null value is not a keyword.
Q29. What is the preferred
size of a component?
The preferred size of a component is the minimum component size that will allow the
component to display normally.
The preferred size of a component is the minimum component size that will allow the
component to display normally.
Q30. What method is used to
specify a container's layout?
The setLayout() method is used to specify a container's layout.
The setLayout() method is used to specify a container's layout.
Q31. Which containers use a FlowLayout as
their default layout?
The Panel and Applet classes use the FlowLayout as their default layout.
The Panel and Applet classes use the FlowLayout as their default layout.
Q32. What state does a thread enter when
it terminates its processing?
When a thread terminates its processing, it enters the dead state.
When a thread terminates its processing, it enters the dead state.
Q33. What is the Collections
API?
The Collections API is a set of classes and interfaces that support operations on collections of objects.
The Collections API is a set of classes and interfaces that support operations on collections of objects.
Q34. Which characters may be used as the
second character
of an identifier, but not as the first character of an identifier?
The digits 0 through 9 may not be used as the first character of an identifier but they may be used after the first character of an identifier.
of an identifier, but not as the first character of an identifier?
The digits 0 through 9 may not be used as the first character of an identifier but they may be used after the first character of an identifier.
Q35. What is the List interface?
The List interface provides support for ordered collections of objects.
The List interface provides support for ordered collections of objects.
Q36. How does Java handle integer
overflows and underflows?
It uses those low order bytes of the result that can fit into the size of the type allowed by the operation.
It uses those low order bytes of the result that can fit into the size of the type allowed by the operation.
Q37. What is the Vector class?
The Vector class provides the capability to implement a growable array of objects
The Vector class provides the capability to implement a growable array of objects
Q38. What modifiers may be used with an
inner class that is a
member of an outer class?
A (non-local) inner class may be declared as public, protected, private, static, final, or abstract.
A (non-local) inner class may be declared as public, protected, private, static, final, or abstract.
Q39. What is an Iterator interface?
The Iterator interface is used to step through the elements of a Collection.
The Iterator interface is used to step through the elements of a Collection.
Q40. What is the difference between the
>> and >>> operators?
The >> operator carries the sign bit when shifting right. The >>> zero-fills bits that have been shifted out.
The >> operator carries the sign bit when shifting right. The >>> zero-fills bits that have been shifted out.
Q41. Which method of the Component class
is used to set the
position and size of a component?
setBounds()
setBounds()
Q42. How many bits are used to represent
Unicode, ASCII, UTF-16,
and UTF-8 characters?
Unicode requires 16 bits and ASCII require 7 bits. Although the ASCII character set uses only 7 bits, it is usually represented as 8 bits. UTF-8 represents characters using 8, 16, and 18 bit patterns. UTF-16 uses 16-bit and larger bit patterns.
Unicode requires 16 bits and ASCII require 7 bits. Although the ASCII character set uses only 7 bits, it is usually represented as 8 bits. UTF-8 represents characters using 8, 16, and 18 bit patterns. UTF-16 uses 16-bit and larger bit patterns.
Q43. What is the difference between
yielding and sleeping?
When a task invokes its yield() method, it returns to the ready state. When a task invokes its sleep() method, it returns to the waiting state.
When a task invokes its yield() method, it returns to the ready state. When a task invokes its sleep() method, it returns to the waiting state.
Q44. Which java.util classes and
interfaces support event handling?
The EventObject class and the EventListener interface support event processing.
The EventObject class and the EventListener interface support event processing.
Q45. Is sizeof a keyword?
The sizeof operator is not a keyword.
The sizeof operator is not a keyword.
Q46. What are wrapped classes?
Wrapped classes are classes that allow primitive types to be accessed as objects.
Wrapped classes are classes that allow primitive types to be accessed as objects.
Q47. Does garbage collection guarantee
that a program will not run
out of memory?
Garbage collection does not guarantee that a program will not run out of memory. It is possible for programs to use up memory resources faster than they are garbage collected. It is also possible for programs to create objects that are not subject to garbage collection
Garbage collection does not guarantee that a program will not run out of memory. It is possible for programs to use up memory resources faster than they are garbage collected. It is also possible for programs to create objects that are not subject to garbage collection
Q48. What restrictions are placed on the
location of a package
statement within a source code file?
A package statement must appear as the first line in a source code file (excluding blank lines and comments).
A package statement must appear as the first line in a source code file (excluding blank lines and comments).
Q49. Can an object's finalize() method be
invoked while it is reachable?
An object's finalize() method cannot be invoked by the garbage collector while the object is still reachable. However, an object's finalize() method may be invoked by other objects.
An object's finalize() method cannot be invoked by the garbage collector while the object is still reachable. However, an object's finalize() method may be invoked by other objects.
Q50. What is the immediate superclass of
the Applet class?
Panel
Panel
Q51. What is the difference between
preemptive scheduling and
time slicing?
Under preemptive scheduling, the highest priority task executes until it enters the waiting or dead states or a higher priority task comes into existence. Under time slicing, a task executes for a predefined slice of time and then reenters the pool of ready tasks. The scheduler then determines which task should execute next, based on priority and other factors.
Under preemptive scheduling, the highest priority task executes until it enters the waiting or dead states or a higher priority task comes into existence. Under time slicing, a task executes for a predefined slice of time and then reenters the pool of ready tasks. The scheduler then determines which task should execute next, based on priority and other factors.
Q52 Name three Component subclasses that
support painting.
The Canvas, Frame, Panel, and Applet classes support painting.
The Canvas, Frame, Panel, and Applet classes support painting.
Q53. What value does readLine() return
when it has reached
the end of a file?
The readLine() method returns null when it has reached the end of a file.
The readLine() method returns null when it has reached the end of a file.
Q54. What is the immediate superclass of
the Dialog class?
Window
Window
Q55. What is clipping?
Clipping is the process of confining paint operations to a limited area or shape.
Clipping is the process of confining paint operations to a limited area or shape.
Q56. What is a native method?
A native method is a method that is implemented in a language other than Java.
A native method is a method that is implemented in a language other than Java.
Q57. Can a for statement loop
indefinitely?
Yes, a for statement can loop indefinitely. For example, consider the following: for(;;) ;
Yes, a for statement can loop indefinitely. For example, consider the following: for(;;) ;
Q58. What are order of precedence and
associativity, and how are
they used?
Order of precedence determines the order in which operators are evaluated in expressions. Associatity determines whether an expression is evaluated left-to-right or right-to-left
Order of precedence determines the order in which operators are evaluated in expressions. Associatity determines whether an expression is evaluated left-to-right or right-to-left
Q59. When a thread blocks on I/O, what
state does it enter?
A thread enters the waiting state when it blocks on I/O.
A thread enters the waiting state when it blocks on I/O.
Q60. To what value is a variable of the
String type automatically
initialized?
The default value of an String type is null.
The default value of an String type is null.
Q61. What is the catch or declare rule for
method declarations?
If a checked exception may be thrown within the body of a method, the method must either catch the exception or declare it in its throws clause.
If a checked exception may be thrown within the body of a method, the method must either catch the exception or declare it in its throws clause.
Q62. What is the difference between a
MenuItem and a CheckboxMenuItem?
The CheckboxMenuItem class extends the MenuItem class to support a menu item that may be checked or unchecked.
The CheckboxMenuItem class extends the MenuItem class to support a menu item that may be checked or unchecked.
Q63. What is a task's priority and how is
it used in scheduling?
A task's priority is an integer value that identifies the relative order in which it should be executed with respect to other tasks. The scheduler attempts to schedule higher priority tasks before lower priority tasks.
A task's priority is an integer value that identifies the relative order in which it should be executed with respect to other tasks. The scheduler attempts to schedule higher priority tasks before lower priority tasks.
Q64. What class is the top of the AWT
event hierarchy?
The java.awt.AWTEvent class is the highest-level class in the AWT event-class hierarchy.
The java.awt.AWTEvent class is the highest-level class in the AWT event-class hierarchy.
Q65. When a thread is created and started,
what is its initial state?
A thread is in the ready state after it has been created and started.
A thread is in the ready state after it has been created and started.
Q66. Can an anonymous class be declared as
implementing an
interface and extending a class?
An anonymous class may implement an interface or extend a superclass, but may not be declared to do both.
An anonymous class may implement an interface or extend a superclass, but may not be declared to do both.
Q67. What is the range of the short type?
The range of the short type is -(2^15) to 2^15 - 1.
The range of the short type is -(2^15) to 2^15 - 1.
Q68. What is the range of the char type?
The range of the char type is 0 to 2^16 - 1.
The range of the char type is 0 to 2^16 - 1.
Q69. In which package are most of the AWT
events that support
the event-delegation model defined?
Most of the AWT-related events of the event-delegation model are defined in the java.awt.event package. The AWTEvent class is defined in the java.awt package.
Most of the AWT-related events of the event-delegation model are defined in the java.awt.event package. The AWTEvent class is defined in the java.awt package.
Q70. What is the immediate superclass of
Menu?
MenuItem
MenuItem
Q71. What is the purpose of finalization?
The purpose of finalization is to give an unreachable object the opportunity to perform any cleanup processing before the object is garbage collected.
The purpose of finalization is to give an unreachable object the opportunity to perform any cleanup processing before the object is garbage collected.
Q72. Which class is the immediate
superclass of the MenuComponent
class.
Object
Object
Q73. What invokes a thread's
run() method?
After a thread is started, via its start() method or that of the Thread class, the JVM invokes the thread's run() method when the thread is initially executed.
After a thread is started, via its start() method or that of the Thread class, the JVM invokes the thread's run() method when the thread is initially executed.
Q74. What is the difference between the
Boolean & operator and the
&& operator?
If an expression involving the Boolean & operator is evaluated, both operands are
evaluated. Then the & operator is applied to the operand. When an expression involving the && operator is evaluated, the first operand is evaluated. If the first operand returns a value of true then the second operand is evaluated. The && operator is then applied to the first and second operands. If the first operand evaluates to false, the evaluation of the second operand is skipped.
If an expression involving the Boolean & operator is evaluated, both operands are
evaluated. Then the & operator is applied to the operand. When an expression involving the && operator is evaluated, the first operand is evaluated. If the first operand returns a value of true then the second operand is evaluated. The && operator is then applied to the first and second operands. If the first operand evaluates to false, the evaluation of the second operand is skipped.
Q75. Name three subclasses of the
Component class.
Box.Filler, Button, Canvas, Checkbox, Choice, Container, Label, List, Scrollbar, or TextComponent
Box.Filler, Button, Canvas, Checkbox, Choice, Container, Label, List, Scrollbar, or TextComponent
Q76. What is the GregorianCalendar class?
The GregorianCalendar provides support for traditional Western calendars.
The GregorianCalendar provides support for traditional Western calendars.
Q77. Which Container method is used to
cause a container to be
laid out and redisplayed?
validate()
validate()
Q78. What is the purpose of the Runtime
class?
The purpose of the Runtime class is to provide access to the Java runtime system.
The purpose of the Runtime class is to provide access to the Java runtime system.
Q79. How many times may an object's
finalize() method be invoked
by the garbage collector?
An object's finalize() method may only be invoked once by the garbage collector.
An object's finalize() method may only be invoked once by the garbage collector.
Q80. What is the purpose of the finally
clause of a try-catchfinally statement?
The finally clause is used to provide the capability to execute code no matter whether or not an exception is thrown or caught.
The finally clause is used to provide the capability to execute code no matter whether or not an exception is thrown or caught.
Q81. What is the argument type of a
program's main() method?
A program's main() method takes an argument of the String[] type.
A program's main() method takes an argument of the String[] type.
Q82. Which Java operator is right
associative?
The = operator is right associative.
The = operator is right associative.
Q83. What is the Locale class?
The Locale class is used to tailor program output to the conventions of a particular geographic, political, or cultural region.
The Locale class is used to tailor program output to the conventions of a particular geographic, political, or cultural region.
Q84. Can a double value be cast to a byte?
Yes, a double value can be cast to a byte.
Yes, a double value can be cast to a byte.
Q85. What is the difference between a
break statement and a
continue statement?
A break statement results in the termination of the statement to which it applies (switch, for, do, or while). A continue statement is used to end the current loop iteration and return control to the loop statement.
A break statement results in the termination of the statement to which it applies (switch, for, do, or while). A continue statement is used to end the current loop iteration and return control to the loop statement.
Q86. What must a class do to implement an
interface?
It must provide all of the methods in the interface and identify the interface in its implements clause.
It must provide all of the methods in the interface and identify the interface in its implements clause.
Q87. What method is invoked to cause an
object to begin executing
as a separate thread?
The start() method of the Thread class is invoked to cause an object to begin executing as a separate thread.
The start() method of the Thread class is invoked to cause an object to begin executing as a separate thread.
Q88. Name two subclasses of the
TextComponent class.
TextField and TextArea
TextField and TextArea
Q89. What is the advantage of the
event-delegation model over
the earlier eventinheritance model?
The event-delegation model has two advantages over the event-inheritance model. First, it enables event handling to be handled by objects other than the ones that generate the events (or their containers). This allows a clean separation between a component's design and its use. The other advantage of the event-delegation model is that it performs much better in applications where many events are generated. This performance improvement is due to the fact that the event-delegation model does not have to repeatedly process unhandled events, as is the case of the event-inheritance model.
The event-delegation model has two advantages over the event-inheritance model. First, it enables event handling to be handled by objects other than the ones that generate the events (or their containers). This allows a clean separation between a component's design and its use. The other advantage of the event-delegation model is that it performs much better in applications where many events are generated. This performance improvement is due to the fact that the event-delegation model does not have to repeatedly process unhandled events, as is the case of the event-inheritance model.
Q90. Which containers may have a MenuBar?
Frame
Frame
Q91. How are commas used in the
intialization and iteration parts
of a for statement?
Commas are used to separate multiple statements within the initialization and iteration parts of a for statement.
Commas are used to separate multiple statements within the initialization and iteration parts of a for statement.
Q92. What is the purpose of the wait(),
notify(), and notifyAll()
methods?
The wait(),notify(), and notifyAll() methods are used to provide an efficient way for threads to wait for a shared resource. When a thread executes an object's wait() method, it enters the waiting state. It only enters the ready state after another thread invokes the object's notify() or notifyAll() methods..
The wait(),notify(), and notifyAll() methods are used to provide an efficient way for threads to wait for a shared resource. When a thread executes an object's wait() method, it enters the waiting state. It only enters the ready state after another thread invokes the object's notify() or notifyAll() methods..
Q93. What is an abstract
method?
An abstract method is a method whose implementation is deferred to a subclass.
An abstract method is a method whose implementation is deferred to a subclass.
Q94. How are Java source code
files named?
A Java source code file takes the name of a public class or interface that is defined within the file. A source code file may contain at most one public class or interface. If a public class or interface is defined within a source code file, then the source code file must take the name of the public class or interface. If no public class or interface is defined within a source code file, then the file must take on a name that is different than its classes and interfaces. Source code files use the .java extension.
A Java source code file takes the name of a public class or interface that is defined within the file. A source code file may contain at most one public class or interface. If a public class or interface is defined within a source code file, then the source code file must take the name of the public class or interface. If no public class or interface is defined within a source code file, then the file must take on a name that is different than its classes and interfaces. Source code files use the .java extension.
Q95. What is the relationship between the
Canvas class and the
Graphics class?
A Canvas object provides access to a Graphics object via its paint() method.
A Canvas object provides access to a Graphics object via its paint() method.
Q96. What are the high-level thread
states?
The high-level thread states are ready, running, waiting, and dead.
The high-level thread states are ready, running, waiting, and dead.
Q97. What value does read() return when it
has reached the end of
a file?
The read() method returns -1 when it has reached the end of a file.
The read() method returns -1 when it has reached the end of a file.
Q98. Can a Byte object be cast to a double
value?
No, an object cannot be cast to a primitive value.
No, an object cannot be cast to a primitive value.
Q99. What is the difference between a
static and a nonstatic inner
class?
A non-static inner class may have object instances that are associated with instances of the class's outer class. A static inner class does not have any object instances.
A non-static inner class may have object instances that are associated with instances of the class's outer class. A static inner class does not have any object instances.
Q100. What is the difference between the
String and StringBuffer
classes?
String objects are constants. StringBuffer objects are not.
String objects are constants. StringBuffer objects are not.
Q101. If a variable is declared as
private, where may the variable
be accessed?
A private variable may only be accessed within the class in which it is declared.
A private variable may only be accessed within the class in which it is declared.
Q102. What is an object's lock and which
object's have locks?
An object's lock is a mechanism that is used by multiple threads to obtain synchronized access to the object. A thread may execute a synchronized method of an object only after it has acquired the object's lock. All objects and classes have locks. A class's lock is acquired on the class's Class object.
An object's lock is a mechanism that is used by multiple threads to obtain synchronized access to the object. A thread may execute a synchronized method of an object only after it has acquired the object's lock. All objects and classes have locks. A class's lock is acquired on the class's Class object.
Q103. What is the Dictionary class?
The Dictionary class provides the capability to store key-value pairs.
The Dictionary class provides the capability to store key-value pairs.
Q104. How are the elements of a
BorderLayout organized?
The elements of a BorderLayout are organized at the borders (North, South, East, and West) and the center of a container.
The elements of a BorderLayout are organized at the borders (North, South, East, and West) and the center of a container.
Q105. What is the % operator?
It is referred to as the modulo or remainder operator. It returns the remainder of dividing the first operand by the second operand.
It is referred to as the modulo or remainder operator. It returns the remainder of dividing the first operand by the second operand.
Q106. When can an object reference be cast
to an interface reference?
An object reference be cast to an interface reference when the object implements the referenced interface.
An object reference be cast to an interface reference when the object implements the referenced interface.
Q107. What is the difference between a
Window and a Frame?
The Frame class extends Window to define a main application window that can have a menu bar.
The Frame class extends Window to define a main application window that can have a menu bar.
Q108. Which class is extended by all other
classes?
The Object class is extended by all other classes.
The Object class is extended by all other classes.
Q109. Can an object be garbage collected
while it is still reachable?
A reachable object cannot be garbage collected. Only unreachable objects may be garbage collected..
A reachable object cannot be garbage collected. Only unreachable objects may be garbage collected..
Q110. Is the ternary operator written x :
y ? z or x ? y : z ?
It is written x ? y : z.
It is written x ? y : z.
Q111. What is the difference between the
Font and FontMetrics
classes?
The FontMetrics class is used to define implementation-specific properties, such as ascent and descent, of a Font object.
The FontMetrics class is used to define implementation-specific properties, such as ascent and descent, of a Font object.
Q112. How is rounding performed under
integer division?
The fractional part of the result is truncated. This is known as rounding toward zero.
The fractional part of the result is truncated. This is known as rounding toward zero.
Q113. What happens when a thread cannot
acquire a lock on an
object?
If a thread attempts to execute a synchronized method or synchronized statement and is unable to acquire an object's lock, it enters the waiting state until the lock becomes available.
If a thread attempts to execute a synchronized method or synchronized statement and is unable to acquire an object's lock, it enters the waiting state until the lock becomes available.
Q114. What is the difference
between the Reader/Writer class
hierarchy and the InputStream/OutputStream classhierarchy?
The Reader/Writer class
hierarchy is character-oriented, and the InputStream/ OutputStream class
hierarchy is byte-oriented.
Q115. What classes of exceptions may be
caught by a catch clause?
A catch clause can catch any exception that may be assigned to the Throwable type. This includes the Error and Exception types.
A catch clause can catch any exception that may be assigned to the Throwable type. This includes the Error and Exception types.
Q116. If a class is declared without any
access modifiers, where
may the class be accessed?
A class that is declared without any access modifiers is said to have package access. This means that the class can only be accessed by other classes and interfaces that are defined within the same package.
A class that is declared without any access modifiers is said to have package access. This means that the class can only be accessed by other classes and interfaces that are defined within the same package.
Q117. What is the
SimpleTimeZone class?
The SimpleTimeZone class provides support for a Gregorian calendar.
The SimpleTimeZone class provides support for a Gregorian calendar.
Q118. What is the Map interface?
The Map interface replaces the JDK 1.1 Dictionary class and is used associate keys with values.
The Map interface replaces the JDK 1.1 Dictionary class and is used associate keys with values.
Q119. Does a class inherit the
constructors of its superclass?
A class does not inherit constructors from any of its superclasses.
A class does not inherit constructors from any of its superclasses.
Q120. For which statements does it make
sense to use a label?
The only statements for which it makes sense to use a label are those statements that can enclose a break or continue statement.
The only statements for which it makes sense to use a label are those statements that can enclose a break or continue statement.
Q121. What is the purpose of
the System class?
The purpose of the System class is to provide access to system resources.
The purpose of the System class is to provide access to system resources.
Q122. Which TextComponent method is used
to set a TextComponent
to the read-only state?
setEditable()
setEditable()
Q123. How are the elements of a CardLayout
organized?
The elements of a CardLayout are stacked, one on top of the other, like a deck of cards.
The elements of a CardLayout are stacked, one on top of the other, like a deck of cards.
Q124. Is &&= a valid Java
operator?
No, it is not.
No, it is not.
Q125. Name the eight primitive
Java types?
The eight primitive types are byte, char, short, int, long, float, double, and boolean.
The eight primitive types are byte, char, short, int, long, float, double, and boolean.
Q126. Which class should you use to obtain
design information
about an object?
The Class class is used to obtain information about an object's design.
The Class class is used to obtain information about an object's design.
Q127. What is the relationship between
clipping and repainting?
When a window is repainted by the AWT painting thread, it sets the clipping regions to the area of the window that requires repainting.
When a window is repainted by the AWT painting thread, it sets the clipping regions to the area of the window that requires repainting.
Q128. Is "abc" a primitive
value?
The String literal "abc" is not a primitive value. It is a String object.
The String literal "abc" is not a primitive value. It is a String object.
Q129. What is the relationship between an
event-listener interface
and an event-adapter class?
An event-listener interface defines the methods that must be implemented by an event handler for a particular kind of event. An event adapter provides a default implementation of an event-listener interface.
An event-listener interface defines the methods that must be implemented by an event handler for a particular kind of event. An event adapter provides a default implementation of an event-listener interface.
Q130. What restrictions are placed on the values
of each case of
a switch statement?
During compilation, the values of each case of a switch statement must evaluate to a value that can be promoted to an int value.
During compilation, the values of each case of a switch statement must evaluate to a value that can be promoted to an int value.
Q131. What modifiers may be used with an
interface declaration?
An interface may be declared as public or abstract.
An interface may be declared as public or abstract.
Q132. Is a class a subclass of itself?
A class is a subclass of itself.
A class is a subclass of itself.
Q133. What is the highest-level event
class of the eventdelegation model?
The java.util.EventObject class is the highest-level class in the event-delegation class hierarchy.
The java.util.EventObject class is the highest-level class in the event-delegation class hierarchy.
Q134. What event results from the clicking
of a button?
The ActionEvent event is generated as the result of the clicking of a button.
The ActionEvent event is generated as the result of the clicking of a button.
Q135. How can a GUI component handle its
own events?
A component can handle its own events by implementing the required event-listener interface and adding itself as its own event listener.
A component can handle its own events by implementing the required event-listener interface and adding itself as its own event listener.
Q136. What is the difference between a
while statement and a
do statement?
A while statement checks at the beginning of a loop to see whether the next loop iteration should occur. A do statement checks at the end of a loop to see whether the next iteration of a loop should occur. The do statement will always execute the body of a loop at least once
A while statement checks at the beginning of a loop to see whether the next loop iteration should occur. A do statement checks at the end of a loop to see whether the next iteration of a loop should occur. The do statement will always execute the body of a loop at least once
Q137. How are the elements of
a GridBagLayout organized?
The elements of a GridBagLayout are organized according to a grid. However, the elements are of different sizes and may occupy more than one row or column of the grid. In addition, the rows and columns may have different sizes.
The elements of a GridBagLayout are organized according to a grid. However, the elements are of different sizes and may occupy more than one row or column of the grid. In addition, the rows and columns may have different sizes.
Q138. What advantage do Java's layout managers
provide over
traditional windowing systems?
Java uses layout managers to lay out components in a consistent manner across all windowing platforms. Since Java's layout managers aren't tied to absolute sizing and positioning, they are able to accomodate platform-specific differences among windowing systems.
Java uses layout managers to lay out components in a consistent manner across all windowing platforms. Since Java's layout managers aren't tied to absolute sizing and positioning, they are able to accomodate platform-specific differences among windowing systems.
Q139. What is the Collection
interface?
The Collection interface provides support for the implementation of a mathematical bag – an unordered collection of objects that may contain duplicates.
The Collection interface provides support for the implementation of a mathematical bag – an unordered collection of objects that may contain duplicates.
Q140. What modifiers can be used with a
local inner class?
A local inner class may be final or abstract.
A local inner class may be final or abstract.
Q141. What is the difference between
static and non-staticvariables?
A static variable is associated with the class as a whole rather than with specific instances of a class. Non-static variables take on unique values with each object instance.
A static variable is associated with the class as a whole rather than with specific instances of a class. Non-static variables take on unique values with each object instance.
Q142. What is the difference between the
paint() and repaint()
methods?
The paint() method supports painting via a Graphics object. The repaint() method is used to cause paint() to be invoked by the AWT painting thread.
The paint() method supports painting via a Graphics object. The repaint() method is used to cause paint() to be invoked by the AWT painting thread.
Q143. What is the purpose of the File
class?
The File class is used to create objects that provide access to the files and directories of a local file system.
The File class is used to create objects that provide access to the files and directories of a local file system.
Q144. Can an exception be rethrown?
Yes, an exception can be rethrown.
Yes, an exception can be rethrown.
Q145. Which Math method is used to
calculate the absolute value
of a number?
The abs() method is used to calculate absolute values.
The abs() method is used to calculate absolute values.
Q146. How does multithreading
take place on a computer with a single CPU?
The operating system's task
scheduler allocates execution time to multiple tasks. By quickly switching
between executing tasks, it creates the impression that tasks execute
sequentially.
Q147. When does the compiler supply a
default constructor for a
class?
The compiler supplies a default constructor for a class if no other constructors are provided.
The compiler supplies a default constructor for a class if no other constructors are provided.
Q148. When is the finally clause of a
try-catch-finally statement
executed?
The finally clause of the try-catch-finally statement is always executed unless the thread of execution terminates or an exception occurs within the execution of the finally clause.
The finally clause of the try-catch-finally statement is always executed unless the thread of execution terminates or an exception occurs within the execution of the finally clause.
Q149. Which class is the immediate
superclass of the Container
class?
Component
Component
Q150. If a method is declared as
protected, where may the method
be accessed?
A protected method may only be accessed by classes or interfaces of the same package or by subclasses of the class in which it is declared.
A protected method may only be accessed by classes or interfaces of the same package or by subclasses of the class in which it is declared.
Q151. How can the Checkbox class be used
to create a radio button?
By associating Checkbox objects with a CheckboxGroup.
By associating Checkbox objects with a CheckboxGroup.
Q152. Which non-Unicode letter characters
may be used as the
first character of an identifier?
The non-Unicode letter characters $ and _ may appear as the first character of an identifier
The non-Unicode letter characters $ and _ may appear as the first character of an identifier
Q153. What restrictions are
placed on method overloading?
Two methods may not have the same name and argument list but different return types.
Two methods may not have the same name and argument list but different return types.
Q154. What happens when you invoke a
thread's interrupt method
while it is sleeping or waiting?
When a task's interrupt() method is executed, the task enters the ready state. The next time the task enters the running state, an InterruptedException is thrown.
When a task's interrupt() method is executed, the task enters the ready state. The next time the task enters the running state, an InterruptedException is thrown.
Q155. What is casting?
There are two types of casting, casting between primitive numeric types and casting between object references. Casting between numeric types is used to convert larger values, such as double values, to smaller values, such as byte values. Casting between object references is used to refer to an object by a compatible class, interface, or array type reference.
There are two types of casting, casting between primitive numeric types and casting between object references. Casting between numeric types is used to convert larger values, such as double values, to smaller values, such as byte values. Casting between object references is used to refer to an object by a compatible class, interface, or array type reference.
Q156. What is the return type of a
program's main() method?
A program's main() method has a void return type.
A program's main() method has a void return type.
Q157. Name four Container
classes.
Window, Frame, Dialog, FileDialog, Panel, Applet, or ScrollPane
Window, Frame, Dialog, FileDialog, Panel, Applet, or ScrollPane
Q158. What is the difference between a
Choice and a List?
A Choice is displayed in a compact form that requires you to pull it down to see the list of available choices. Only one item may be selected from a Choice. A List may be displayed in such a way that several List items are visible. A List supports the selection of one or more List items.
A Choice is displayed in a compact form that requires you to pull it down to see the list of available choices. Only one item may be selected from a Choice. A List may be displayed in such a way that several List items are visible. A List supports the selection of one or more List items.
Q159. What class of exceptions are
generated by the Java run-time
system?
The Java runtime system generates RuntimeException and Error exceptions.
The Java runtime system generates RuntimeException and Error exceptions.
Q160. What class allows you to read
objects directly from a stream?
The ObjectInputStream class supports the reading of objects from input streams.
The ObjectInputStream class supports the reading of objects from input streams.
Q161. What is the difference between a
field variable and a local
variable?
A field variable is a variable that is declared as a member of a class. A local variable is a variable that is declared local to a method.
A field variable is a variable that is declared as a member of a class. A local variable is a variable that is declared local to a method.
Q162. Under what conditions is an object's
finalize() method
invoked by the garbage collector?
The garbage collector invokes an object's finalize() method when it detects that the object has become unreachable.
The garbage collector invokes an object's finalize() method when it detects that the object has become unreachable.
Q163. How are this() and super() used with
constructors?
this() is used to invoke a constructor of the same class. super() is used to invoke a superclass constructor.
this() is used to invoke a constructor of the same class. super() is used to invoke a superclass constructor.
Q164. What is the relationship between a
method's throws clause
and the exceptions that can be thrown during themethod's execution?
A method's throws clause must declare any checked exceptions that are not caught within the body of the method.
A method's throws clause must declare any checked exceptions that are not caught within the body of the method.
Q165. What is the difference between the
JDK 1.02 event model
and the event-delegation model introduced withJDK 1.1?
The JDK 1.02 event model uses an event inheritance or bubbling approach. In this model, components are required to handle their own events. If they do not handle a particular event, the event is inherited by (or bubbled up to) the component's container. The container then either handles the event or it is bubbled up to its container and so on, until the highest-level container has been tried..In the event-delegation model, specific objects are designated as event handlers for GUI components. These objects implement event-listener interfaces. The event-delegation model is more efficient than the event-inheritance model because it eliminates the processing required to support the bubbling of unhandled events.
The JDK 1.02 event model uses an event inheritance or bubbling approach. In this model, components are required to handle their own events. If they do not handle a particular event, the event is inherited by (or bubbled up to) the component's container. The container then either handles the event or it is bubbled up to its container and so on, until the highest-level container has been tried..In the event-delegation model, specific objects are designated as event handlers for GUI components. These objects implement event-listener interfaces. The event-delegation model is more efficient than the event-inheritance model because it eliminates the processing required to support the bubbling of unhandled events.
Q166. How is it possible for two String
objects with identical
values not to be equal under the == operator?
The == operator compares two objects to determine if they are the same object in memory. It is possible for two String objects to have the same value, but located indifferent areas of memory.
The == operator compares two objects to determine if they are the same object in memory. It is possible for two String objects to have the same value, but located indifferent areas of memory.
Q167. Why are the methods of the Math
class static?
So they can be invoked as if they are a mathematical code library.
So they can be invoked as if they are a mathematical code library.
Q168. What Checkbox method allows you to
tell if a Checkbox
is checked?
getState()
getState()
Q169. What state is a thread
in when it is executing?
An executing thread is in the running state.
An executing thread is in the running state.
Q170. What are the legal operands of the
instanceof operator?
The left operand is an object reference or null value and the right operand is a class, interface, or array type.
The left operand is an object reference or null value and the right operand is a class, interface, or array type.
Q171. How are the elements of a GridLayout
organized?
The elements of a GridBad layout are of equal size and are laid out using the squares of a grid.
The elements of a GridBad layout are of equal size and are laid out using the squares of a grid.
Q172. What an I/O filter?
An I/O filter is an object that reads from one stream and writes to another, usually altering the data in some way as it is passed from one stream to another.
An I/O filter is an object that reads from one stream and writes to another, usually altering the data in some way as it is passed from one stream to another.
Q173. If an object is garbage collected,
can it become reachable
again?
Once an object is garbage collected, it ceases to exist. It can no longer become reachable again.
Once an object is garbage collected, it ceases to exist. It can no longer become reachable again.
Q174. What is the Set
interface?
The Set interface provides
methods for accessing the elements of a finite mathematical set. Sets do not
allow duplicate elements.
Q175. What classes of exceptions may be
thrown by a throw statement?
A throw statement may throw any expression that may be assigned to the Throwable type.
A throw statement may throw any expression that may be assigned to the Throwable type.
Q176. What are E and PI?
E is the base of the natural logarithm and PI is mathematical value pi.
E is the base of the natural logarithm and PI is mathematical value pi.
Q177. Are true and false
keywords?
The values true and false are not keywords.
The values true and false are not keywords.
Q178. What is a void return type?
A void return type indicates that a method does not return a value.
A void return type indicates that a method does not return a value.
Q179. What is the purpose of the
enableEvents() method?
The enableEvents() method is used to enable an event for a particular object. Normally, an event is enabled when a listener is added to an object for a particular event. The enableEvents() method is used by objects that handle events by overriding their eventdispatch methods.
The enableEvents() method is used to enable an event for a particular object. Normally, an event is enabled when a listener is added to an object for a particular event. The enableEvents() method is used by objects that handle events by overriding their eventdispatch methods.
Q180. What is the difference between the
File and RandomAccessFile
classes?
The File class encapsulates the files and directories of the local file system. The RandomAccessFile class provides the methods needed to directly access data contained in any part of a file.
The File class encapsulates the files and directories of the local file system. The RandomAccessFile class provides the methods needed to directly access data contained in any part of a file.
Q181. What happens when you add a double
value to a String?
The result is a String object.
The result is a String object.
Q182. What is your platform's default
character encoding?
If you are running Java on English Windows platforms, it is probably Cp1252. If you are running Java on English Solaris platforms, it is most likely 8859_1..
If you are running Java on English Windows platforms, it is probably Cp1252. If you are running Java on English Solaris platforms, it is most likely 8859_1..
Q183. Which package is always imported by
default?
The java.lang package is always imported by default.
The java.lang package is always imported by default.
Q184. What interface must an object
implement before it can be
written to a stream as an object?
An object must implement the Serializable or Externalizable interface before it can be written to a stream as an object.
An object must implement the Serializable or Externalizable interface before it can be written to a stream as an object.
Q185. How are this and super
used?
this is used to refer to the current object instance. super is used to refer to the variables and methods of the superclass of the current object instance.
this is used to refer to the current object instance. super is used to refer to the variables and methods of the superclass of the current object instance.
Q186. What is the purpose of garbage
collection?
The purpose of garbage collection is to identify and discard objects that are no longer needed by a program so that their resources may be reclaimed and reused.
The purpose of garbage collection is to identify and discard objects that are no longer needed by a program so that their resources may be reclaimed and reused.
Q187. What is a compilation unit?
A compilation unit is a Java source code file.
A compilation unit is a Java source code file.
Q188. What interface is extended by AWT
event listeners?
All AWT event listeners extend the java.util.EventListener interface.
All AWT event listeners extend the java.util.EventListener interface.
Q189. What restrictions are
placed on method overriding?
• Overridden methods must have the same name, argument list, and return type.
• The overriding method may not limit the access of the method it overrides.
• The overriding method may not throw any exceptions that may not be thrownby the overridden method.
• Overridden methods must have the same name, argument list, and return type.
• The overriding method may not limit the access of the method it overrides.
• The overriding method may not throw any exceptions that may not be thrownby the overridden method.
Q190. How can a dead thread be
restarted?
A dead thread cannot be restarted.
A dead thread cannot be restarted.
Q191. What happens if an exception is not
caught?
An uncaught exception results in the uncaughtException() method of the thread's
ThreadGroup being invoked, which eventually results in the termination of the program in which it is thrown.
An uncaught exception results in the uncaughtException() method of the thread's
ThreadGroup being invoked, which eventually results in the termination of the program in which it is thrown.
Q192. What is a layout manager?
A layout manager is an object that is used to organize components in a container.
A layout manager is an object that is used to organize components in a container.
Q193. Which arithmetic operations can
result in the throwing
of an ArithmeticException?
Integer / and % can result in the throwing of an ArithmeticException.
Integer / and % can result in the throwing of an ArithmeticException.
Q194. What are three ways in which a
thread can enter the waiting
state?
A thread can enter the waiting state by invoking its sleep() method, by blocking on I/O, by unsuccessfully attempting to acquire an object's lock, or by invoking an object's wait() method. It can also enter the waiting state by invoking its (deprecated) suspend() method.
A thread can enter the waiting state by invoking its sleep() method, by blocking on I/O, by unsuccessfully attempting to acquire an object's lock, or by invoking an object's wait() method. It can also enter the waiting state by invoking its (deprecated) suspend() method.
Q195. Can an abstract class be final?
An abstract class may not be declared as final.
An abstract class may not be declared as final.
Q196. What is the
ResourceBundle class?
The
ResourceBundle class is used to store locale-specific resources that can be
loaded by a program to tailor the program's appearance to the particular locale
in which it is being run.
Q197. What happens if a try-catch-finally
statement doesnot have a catch clause to handle an exception that is
thrown within the body of the try statement?
The exception propagates up to the next higher level try-catch statement (if any) or results in the program's termination.
thrown within the body of the try statement?
The exception propagates up to the next higher level try-catch statement (if any) or results in the program's termination.
Q198. What is numeric promotion?
Numeric promotion is the conversion of a smaller numeric type to a larger numeric type, so that integer and floating-point operations may take place. In numerical promotion, byte, char, and short values are converted to int values. The int values are also converted to long values, if necessary. The long and float values are converted to double values, as required.
Numeric promotion is the conversion of a smaller numeric type to a larger numeric type, so that integer and floating-point operations may take place. In numerical promotion, byte, char, and short values are converted to int values. The int values are also converted to long values, if necessary. The long and float values are converted to double values, as required.
Q199. What is the difference between a
Scrollbar and a ScrollPane?
A Scrollbar is a Component, but not a Container. A ScrollPane is a Container. A ScrollPane handles its own events and performs its own scrolling.
A Scrollbar is a Component, but not a Container. A ScrollPane is a Container. A ScrollPane handles its own events and performs its own scrolling.
Q200. What is the difference between a
public and a nonpublic class?
A public class may be accessed outside of its package. A non-public class may not be accessed outside of its package.
A public class may be accessed outside of its package. A non-public class may not be accessed outside of its package.
Q201. To what value is a variable of the
boolean type automatically
initialized?
The default value of the boolean type is false.
The default value of the boolean type is false.
Q202. Can try statements be nested?
Try statements may be tested.
Try statements may be tested.
Q203. What is the difference
between the prefix and postfix forms of the ++ operator?
The prefix form performs the
increment operation and returns the value of the increment operation. The
postfix form returns the current value all of the expression and then performs
the increment operation on that value.
Q204. What is the purpose of a statement
block?
A statement block is used to organize a sequence of statements as a single statement group.
A statement block is used to organize a sequence of statements as a single statement group.
Q205.
What is a Java package and how is it used?
A Java package is a naming context for classes and interfaces. A package is used to create a separate name space for groups of classes and interfaces. Packages are also used to organize related classes and interfaces into a single API unit and to control accessibility to these classes and interfaces.
A Java package is a naming context for classes and interfaces. A package is used to create a separate name space for groups of classes and interfaces. Packages are also used to organize related classes and interfaces into a single API unit and to control accessibility to these classes and interfaces.
Q206. What modifiers may be used with a top-level class?
A top-level class may be public, abstract, or final.
A top-level class may be public, abstract, or final.
Q207. What are the Object and Class classes used for?
The Object class is the highest-level class in the Java class hierarchy. The Class class is used to represent the classes and interfaces that are loaded by a Java program..
The Object class is the highest-level class in the Java class hierarchy. The Class class is used to represent the classes and interfaces that are loaded by a Java program..
Q208. How does a try statement determine which catch clause should be used to handle
an exception?
When an exception is thrown within the body of a try statement, the catch clauses of the try statement are examined in the order in which they appear. The first catch clause that is capable of handling the exception is executed. The remaining catch clauses are ignored.
When an exception is thrown within the body of a try statement, the catch clauses of the try statement are examined in the order in which they appear. The first catch clause that is capable of handling the exception is executed. The remaining catch clauses are ignored.
Q209. Can an unreachable
object become reachable again?
An unreachable object may become reachable again. This can happen when the object's finalize() method is invoked and the object performs an operation which causes it to become accessible to reachable objects.
An unreachable object may become reachable again. This can happen when the object's finalize() method is invoked and the object performs an operation which causes it to become accessible to reachable objects.
Q210. When is an object subject to garbage
collection?
An object is subject to garbage collection when it becomes unreachable to the program in which it is used.
An object is subject to garbage collection when it becomes unreachable to the program in which it is used.
Q211. What method must be implemented by
all threads?
All tasks must implement the run() method, whether they are a subclass of Thread or implement the Runnable interface.
All tasks must implement the run() method, whether they are a subclass of Thread or implement the Runnable interface.
Q212. What methods are used to get and set
the text label displayed
by a Button object?
getLabel() and setLabel()
getLabel() and setLabel()
Q213. Which Component subclass is used for
drawing and painting?
Canvas
Canvas
Q214. What are synchronized methods and
synchronized statements?
Synchronized methods are methods that are used to control access to an object. A thread only executes a synchronized method after it has acquired the lock for the method's object or class. Synchronized statements are similar to synchronized methods. A synchronized statement can only be executed after a thread has acquired the lock for the object or class referenced in the synchronized statement.
Synchronized methods are methods that are used to control access to an object. A thread only executes a synchronized method after it has acquired the lock for the method's object or class. Synchronized statements are similar to synchronized methods. A synchronized statement can only be executed after a thread has acquired the lock for the object or class referenced in the synchronized statement.
Q215. What are the two basic ways in which
classes that can be
run as threads may be defined?
A thread class may be declared as a subclass of Thread, or it may implement the Runnable interface.
A thread class may be declared as a subclass of Thread, or it may implement the Runnable interface.
Q216. What are the problems faced by Java
programmers who
don't use layout managers?
Without layout managers, Java programmers are faced with determining how their GUI will be displayed across multiple windowing systems and finding a common sizing and positioning that will work within the constraints imposed by each windowing system.
Without layout managers, Java programmers are faced with determining how their GUI will be displayed across multiple windowing systems and finding a common sizing and positioning that will work within the constraints imposed by each windowing system.
Q217. What is the difference between an if
statement and a switch
statement?
The if statement is used to select among two alternatives. It uses a boolean expression to decide which alternative should be executed. The switch statement is used to select among multiple alternatives. It uses an int expression to determine which alternative should be executed.
The if statement is used to select among two alternatives. It uses a boolean expression to decide which alternative should be executed. The switch statement is used to select among multiple alternatives. It uses an int expression to determine which alternative should be executed.
Q218. What happens when you add a double
value to a String?
The result is a String object.
The result is a String object.
Q219. What is the List interface?
The List interface provides support for ordered collections of objects.
The List interface provides support for ordered collections of objects.
Q1.What is an Exception?
Ans.An unwanted, unexpected event that disturbs normal flow of the program is called Exception.Example: FileNotFondException.
Ans.An unwanted, unexpected event that disturbs normal flow of the program is called Exception.Example: FileNotFondException.
Q2.What is the purpose of
Exception Handling?
Ans.The main purpose of Exception Handling is for graceful termination of the program.
Q3.What is the meaning of Exception Handling?
Ans. Exception Handling doesn’t mean repairing an Exception, we have to define alternative way to continue rest of the code normally.
Example: If our programming requirement is to read the data from the file locating at London but at Runtime if London file is not available then we have to use local file alternatively to continue rest of program normally. This is nothing but Exception Handling.
Q4.Explain Default Exception Handling Mechanism in java?
Ans.If an exception raised, the method in which it’s raised is responsible for the creation of Exceptions object by including the following information:
Ans.The main purpose of Exception Handling is for graceful termination of the program.
Q3.What is the meaning of Exception Handling?
Ans. Exception Handling doesn’t mean repairing an Exception, we have to define alternative way to continue rest of the code normally.
Example: If our programming requirement is to read the data from the file locating at London but at Runtime if London file is not available then we have to use local file alternatively to continue rest of program normally. This is nothing but Exception Handling.
Q4.Explain Default Exception Handling Mechanism in java?
Ans.If an exception raised, the method in which it’s raised is responsible for the creation of Exceptions object by including the following information:
- Name
of the Exception
- Description
of the Exception
- Stack
Trace
- After
creating Exception object the method handover it to the JVM.
- JVM
checks for Exception Handling code in that method.
- If
the method doesn’t contain any Exception handling code then JVM terminates
the method abnormally and removes the corresponding entry from the stack.
- JVM
identify the caller method and checks for Exception Handling code in that
method. If the caller doesn’t contain any exception handling code then JVM
terminates that method abnormally and removes the corresponding entry from
the stack.
- This
process will be continue until main() method.
- If
the main() method also doesn’t contain exception handling code the JVM
terminates that main() method and removes the corresponding entry from the
stack.
- Just
before terminating the program abnormally JVM handovers the responsibility
of exception handling to the Default Exception Handler which is the
component of JVM.
- Default
Exception Handler just print exception information to the consol in the
following format
Name of Exception: Description
Stack Trace (Location of the Exception)
Stack Trace (Location of the Exception)
Q5.What is the purpose of
try?
Ans We should maintain all risky code inside the try block.
Q6. What is the purpose of catch block?
Ans.We have to maintain all Exception Handling code inside the catch block.
Q7. Is try with multiple catch block is possible?
Ans. The way of handling an exception is varied from exception to exception compulsory we have to write a separate catch block for every exception. Hence try will multiple catch block is possible and it is recommended to use.
Example:
try{
//Risky code
}
catch(IOException e)
{
//Hndling code for IOException
}
catch(ArithmeticException e)
{
//handling code for AE
}
catch(NullPointerExcetpion e)
{
// handling code for NPE
}
catch(Exception e)
{
//default exception handling code
}
Ans We should maintain all risky code inside the try block.
Q6. What is the purpose of catch block?
Ans.We have to maintain all Exception Handling code inside the catch block.
Q7. Is try with multiple catch block is possible?
Ans. The way of handling an exception is varied from exception to exception compulsory we have to write a separate catch block for every exception. Hence try will multiple catch block is possible and it is recommended to use.
Example:
try{
//Risky code
}
catch(IOException e)
{
//Hndling code for IOException
}
catch(ArithmeticException e)
{
//handling code for AE
}
catch(NullPointerExcetpion e)
{
// handling code for NPE
}
catch(Exception e)
{
//default exception handling code
}
Q8. If try with multiple
catch block present is order of catch blocks important in which order we have
to take?
Ans. If try with multiple catch block present then the order of catch block is very important it should be from child to parent but not from parent to child.
Ans. If try with multiple catch block present then the order of catch block is very important it should be from child to parent but not from parent to child.
Q9. What are various
methods to print Exception information? and differentiate them.
Ans.
Throwable class defines the following method to
print exception or error information .
1. printStackTrace() :- This method print exception information in the following format.
1. printStackTrace() :- This method print exception information in the following format.
Name of the Exception: Description
StackTrace
StackTrace
2.toString():- This
method print exception information in the following format.
Name of the Exception:
Description
3.getMessage():- This
method prints only description of the exception.
Description
Q10.If an exception rised inside catch block
then what will happen?
Ans. If an exception raised inside catch block and it is not part of any try block then it is always abnormal termination.
Q11. Is it possible to take try, catch inside try block?
Ans. Yes, It is possible to take try, catch inside try block. That is nesting of try catch is possible.
Q12.Is it possible to take try, catch inside catch block?
Ans. Yes, It is possible to take try, catch inside catch block.
Ans. If an exception raised inside catch block and it is not part of any try block then it is always abnormal termination.
Q11. Is it possible to take try, catch inside try block?
Ans. Yes, It is possible to take try, catch inside try block. That is nesting of try catch is possible.
Q12.Is it possible to take try, catch inside catch block?
Ans. Yes, It is possible to take try, catch inside catch block.
Q13. Is it possible to
take try without catch?
Ans. Yes, it is possible to take try without catch but compulsory finally block should be available.
Q14. What is the purpose of finally block?
Ans. The main purpose of finally block is, to maintain the cleanup code. This block will execute always.
Q15. Is finally block will be execute always?
Ans. Yes finally block will be executed always irrespective of whether exception raised or not raised whether exceptions are handled or not handle. There is one situation where the finally block won’t be executed if the JVM is going to be shutdown.
Q16. In which situation finally block will not executed?
Ans. There is one situation where the finally block won’t be executed if we are using system.exit(0) explicitly then JVM itself will be shutdown and there is no chance of executing finally block.
Ans. Yes, it is possible to take try without catch but compulsory finally block should be available.
Q14. What is the purpose of finally block?
Ans. The main purpose of finally block is, to maintain the cleanup code. This block will execute always.
Q15. Is finally block will be execute always?
Ans. Yes finally block will be executed always irrespective of whether exception raised or not raised whether exceptions are handled or not handle. There is one situation where the finally block won’t be executed if the JVM is going to be shutdown.
Q16. In which situation finally block will not executed?
Ans. There is one situation where the finally block won’t be executed if we are using system.exit(0) explicitly then JVM itself will be shutdown and there is no chance of executing finally block.
Q17. If return statement
present inside try is finally block will be executed?
Ans. Yes, if return statement present inside try, then also finally block will be executed. finally block will dominate return statement also.
Q18. What is the difference between final, finally and finalize()?
Ans. final:- final is a modifier applicable for variables, methods and classes. final variable means constant and reassignment is not possible. final method means implementation is final in the child classes we can’t override. final classmeans it won’t participate in inheritance and child class creation is not possible.
finally:- It is a block associated with try catch to maintain cleanup code. Finally block will be executed always irrespective of whether exception is raised or not raised or whether the exception is handle or not handle.
finalize():- It is a method, Garbage collector always calls this method just before destroying any object to perform cleanup activities.
Ans. Yes, if return statement present inside try, then also finally block will be executed. finally block will dominate return statement also.
Q18. What is the difference between final, finally and finalize()?
Ans. final:- final is a modifier applicable for variables, methods and classes. final variable means constant and reassignment is not possible. final method means implementation is final in the child classes we can’t override. final classmeans it won’t participate in inheritance and child class creation is not possible.
finally:- It is a block associated with try catch to maintain cleanup code. Finally block will be executed always irrespective of whether exception is raised or not raised or whether the exception is handle or not handle.
finalize():- It is a method, Garbage collector always calls this method just before destroying any object to perform cleanup activities.
Q19. Is it possible to
write any statement between try-catch and finally?
Ans. No, it is not possible to write any statement between try catch and finally. If we will try to write any statement between them then we will get compile time error.
Q20. Is it possible to take two finally blocks for the same try?
Ans. No, it is not possible to take two finally blocks for the same try. If we try to take then we will get compile time error.
Ans. No, it is not possible to write any statement between try catch and finally. If we will try to write any statement between them then we will get compile time error.
Q20. Is it possible to take two finally blocks for the same try?
Ans. No, it is not possible to take two finally blocks for the same try. If we try to take then we will get compile time error.
Q21. Is syntax
try-finally-catch is valid ?
Ans. No, this syntax is not valid. It should be like try-catch-finally then only code will compile.
Q22. What is the purpose of throw?
Ans. Sometimes we can create Exception object explicitly and we can handover that exception object to the JVM explicitly by throw keyword.
The purpose of throw keyword is to handover our created exception object explicitly to the JVM.
Example1:
class Test{
public static void main(String[] args){
System.out.println(10/0);
}
}
In this case ArithmeticException object created implicitly and handover to the JVM automatically by the main method.
Ans. No, this syntax is not valid. It should be like try-catch-finally then only code will compile.
Q22. What is the purpose of throw?
Ans. Sometimes we can create Exception object explicitly and we can handover that exception object to the JVM explicitly by throw keyword.
The purpose of throw keyword is to handover our created exception object explicitly to the JVM.
Example1:
class Test{
public static void main(String[] args){
System.out.println(10/0);
}
}
In this case ArithmeticException object created implicitly and handover to the JVM automatically by the main method.
Example2:
Class Test{
Public static void main(String[] args){
Throw new ArithmeticException(“/by Zero”);
}
}
In this case creation of an exception object and handover to the JVM explicitly by the programmer.
Class Test{
Public static void main(String[] args){
Throw new ArithmeticException(“/by Zero”);
}
}
In this case creation of an exception object and handover to the JVM explicitly by the programmer.
Q23. Is it possible
to throw an Error?
Ans. Yes, It is possible to throw any Throwable type including Error.
Ans. Yes, It is possible to throw any Throwable type including Error.
Q24. Is it possible
to throw any java object?
Ans. No, we can use throw keyword only for throwable objects otherwise we will get compile time error saying incompatible type.
Ans. No, we can use throw keyword only for throwable objects otherwise we will get compile time error saying incompatible type.
Q25. After throw is it
allow to take any statement directly?
Ans. After throw statement we are not allow to place any statement directly violation leads to compile time error saying Unreachable Statement.
Q26. What is the purpose of throws?
Ans. The main purpose of throws keyword is to delegate the responsibilities of exception handling to the caller. It requires in the case of checked exception.
Q27. What is the difference between throw and throws?
Ans. Sometimes we can create Exception object explicitly and we can handover that exception object to the JVM explicitly by throw keyword.The main purpose of throw keyword is to handover our created exception object explicitly to the JVM. The main purpose of throws keyword is to delegate the responsibilities of exception handling to the caller. It requires in the case of checked exception.
Ans. After throw statement we are not allow to place any statement directly violation leads to compile time error saying Unreachable Statement.
Q26. What is the purpose of throws?
Ans. The main purpose of throws keyword is to delegate the responsibilities of exception handling to the caller. It requires in the case of checked exception.
Q27. What is the difference between throw and throws?
Ans. Sometimes we can create Exception object explicitly and we can handover that exception object to the JVM explicitly by throw keyword.The main purpose of throw keyword is to handover our created exception object explicitly to the JVM. The main purpose of throws keyword is to delegate the responsibilities of exception handling to the caller. It requires in the case of checked exception.
Q28. What is the
difference between throw and thrown?
Ans. There is no terminology of thrown in java.
Ans. There is no terminology of thrown in java.
Q29. Is it possible to use
throws keyword for any java class?
Ans. No, we can use throws keyword only for Throwable classes. Otherwise we will get compile time error saying Incompatible types.
Q30. If we are taking catch block for an exception but there is no chance of rising that exception in try then what will happen?
Ans. If there is no chance of raising an exception in try then we are not allow to write catch block for that exception violation leads to compile time error. But this rule is applicable only for fully checked exception.
Q31. Explain Exception Handling keyword?
Ans. Exception Handling keyword:
Try :- To maintain Risky code.
Catch:- To maintain Exception Handling code.
Finally:- To maintain the clean up code.
Throw:- To handover our created exception object to the JVM explicitly.
Throws:- To delegate the responsibilities of Exception Handling to the caller.
Ans. No, we can use throws keyword only for Throwable classes. Otherwise we will get compile time error saying Incompatible types.
Q30. If we are taking catch block for an exception but there is no chance of rising that exception in try then what will happen?
Ans. If there is no chance of raising an exception in try then we are not allow to write catch block for that exception violation leads to compile time error. But this rule is applicable only for fully checked exception.
Q31. Explain Exception Handling keyword?
Ans. Exception Handling keyword:
Try :- To maintain Risky code.
Catch:- To maintain Exception Handling code.
Finally:- To maintain the clean up code.
Throw:- To handover our created exception object to the JVM explicitly.
Throws:- To delegate the responsibilities of Exception Handling to the caller.
Q32. Which class act as
root for entire java Exception hierarchy?
Ans. Throwable class act as root for entire java Exception hierarchy.
Ans. Throwable class act as root for entire java Exception hierarchy.
Q33. What is the
difference between Error and Exception?
Ans. Throwable class contain two child classes.
Exception:- These are mostly caused by our program and are recoverable.
Error:- These are not caused by our program, mostly caused by lake of system resources. These are non recoverable.
Ans. Throwable class contain two child classes.
Exception:- These are mostly caused by our program and are recoverable.
Error:- These are not caused by our program, mostly caused by lake of system resources. These are non recoverable.
Q34. What is
difference between checked exception and unchecked exception?
Ans. The exceptions which are checked by the compiler for smooth execution of the program at Runtime is called checked exception. Example: IOException, InterruptedException.The exceptions which are not checked by the compiler are called unchecked exception. Example: ArithmeticException,RuntimeException.
Q35.What is difference between partially checked and fully checked Exception?
Ans. A checked exception is said to be fully checked if and only if all the child classes also checked otherwise it is called partially checked exception.
Example:
IOException:- fully checked exception
Exception:- partially checked exception
Throwable:- partially checked exception
RuntimeException:- unchecked exception
Ans. The exceptions which are checked by the compiler for smooth execution of the program at Runtime is called checked exception. Example: IOException, InterruptedException.The exceptions which are not checked by the compiler are called unchecked exception. Example: ArithmeticException,RuntimeException.
Q35.What is difference between partially checked and fully checked Exception?
Ans. A checked exception is said to be fully checked if and only if all the child classes also checked otherwise it is called partially checked exception.
Example:
IOException:- fully checked exception
Exception:- partially checked exception
Throwable:- partially checked exception
RuntimeException:- unchecked exception
Q36. What is a customized
Exception?
Ans. Sometimes based on our programming requirement we have to create our own exception such type of exception are called customize Exception.
Example:
TooYoungException
TooOldException
InsufficientFundException
Ans. Sometimes based on our programming requirement we have to create our own exception such type of exception are called customize Exception.
Example:
TooYoungException
TooOldException
InsufficientFundException
Q37. Explain the
process of creating the customized Exception.
Ans. Creating customized Exception:
Class TooYoungException extends RuntimeException{
TooYoungExcetpion(String desc){
Super(desc);
}
}
Class TooOldException extends RuntimeException
{
TooOldException(String desc){
super(desc);
}
}
Class custExcepiton{
Public static void main(String[] args){
Int age=Integer.parseInt(args[0]);
If(age>60)
{
Throw new TooYoungException(“Please wait some more time, definitely you will get best match”);
}
Else if(age<18)
{
Throw new TooOldException(“Your age is already crossed of marriage, no chance to getting marriage”);
}
Else
{
System.out.println(“Congratulation! You will get match details soon by your email”);
}
}
Q38. Explain control flow in try, catch, finally.
Ans. Try{
Statement1;
Statement2;
Statement3;
}
Catch(X e){
Statement4;
}
Finally{
Statement5;
}
Statement6;
Case1:
If there is no Exception then output is
Statement1
Statement2
Statement3
Statement5
Statement6
Normal termination
Case2:
If an exception raised at statement2 and corresponding catch block has matched then output is
Statement1
Statement4
Statement5
Statement5
Normal termination
Case3:
An exception raised at statement2 and corresponding catch has not matched then output is
Statement1
Statement5
Abnormal termination
Case4:
An exception occurs at statement4 it always Abnormal termination but before that finally block will be executed and output is
Statement1
Statement2
Statement5
Abnormal termination
Case5:
If an exception raised at statement5 or statement6, it is always abnormal termination.
Q39. Can you give the most common occurred exception in your previous project.
Ans. NullPointerException, ArrayIndexOutofBoundException, StackOverFlowError, ClassCastException, NoClassDefFoundError, ExceptionInitilizerError, IllegalArgumentException, NumberFormatException, IllegalStateException, AssertionError.
Ans. Creating customized Exception:
Class TooYoungException extends RuntimeException{
TooYoungExcetpion(String desc){
Super(desc);
}
}
Class TooOldException extends RuntimeException
{
TooOldException(String desc){
super(desc);
}
}
Class custExcepiton{
Public static void main(String[] args){
Int age=Integer.parseInt(args[0]);
If(age>60)
{
Throw new TooYoungException(“Please wait some more time, definitely you will get best match”);
}
Else if(age<18)
{
Throw new TooOldException(“Your age is already crossed of marriage, no chance to getting marriage”);
}
Else
{
System.out.println(“Congratulation! You will get match details soon by your email”);
}
}
Q38. Explain control flow in try, catch, finally.
Ans. Try{
Statement1;
Statement2;
Statement3;
}
Catch(X e){
Statement4;
}
Finally{
Statement5;
}
Statement6;
Case1:
If there is no Exception then output is
Statement1
Statement2
Statement3
Statement5
Statement6
Normal termination
Case2:
If an exception raised at statement2 and corresponding catch block has matched then output is
Statement1
Statement4
Statement5
Statement5
Normal termination
Case3:
An exception raised at statement2 and corresponding catch has not matched then output is
Statement1
Statement5
Abnormal termination
Case4:
An exception occurs at statement4 it always Abnormal termination but before that finally block will be executed and output is
Statement1
Statement2
Statement5
Abnormal termination
Case5:
If an exception raised at statement5 or statement6, it is always abnormal termination.
Q39. Can you give the most common occurred exception in your previous project.
Ans. NullPointerException, ArrayIndexOutofBoundException, StackOverFlowError, ClassCastException, NoClassDefFoundError, ExceptionInitilizerError, IllegalArgumentException, NumberFormatException, IllegalStateException, AssertionError.
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