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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. TheenableEvents() method is used by objects that handle events by overriding their eventdispatchmethods.
Sandhya.Kishan
- Jul 26th, 2012
The enableEvents() method is used by objects that handle events by overriding their event-dispatch methods.
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What interface must an object implement before it can be written to astream as an object
An object must implement the Serializable or Externalizable interface before it can bewritten to a stream as an object.
Sandhya.Kishan
- May 3rd, 2012
An object must implement the Serializable or Externalizable interface before it can be written to a stream as an object.
As it is a mechanism with which we can save the state of an object by converting it to a byte stream. -
How are this and super used
This is used to refer to the current object instance. super is used to refer to the variablesand methods of the superclass of the current object instance.
Sandhya.Kishan
- Jul 14th, 2012
Super() refers to the superclass of the class where the super keyword is currently being used.It is used to call the constructor of the superclass in the base class. eg: public class Class1{ public C...
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What is a compilation unit
A compilation unit is a Java source code file.
Sandhya.Kishan
- May 3rd, 2012
The source code for a Java class is called a compilation unit. Normally a compilation unit contains a single class definition and it is named for that class.
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What interface is extended by AWT event listeners
All AWT event listeners extend the java.util.EventListener interface.
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What happens if an exception is not caught
An uncaught exception results in the uncaughtException() method of the thread'sThreadGroup being invoked, which eventually results in the termination of the programin which it is thrown.
Sandhya.Kishan
- Jul 14th, 2012
When an exception is not caught by any method then the main method throws an exception and results in the termination of that method.
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What is a layout manager
A layout manager is an object that is used to organize components in a container.
Sandhya.Kishan
- May 3rd, 2012
The arrangement of the components in the container is determined by the layout manager.
Example:When we add a component to an applet or a container, the container uses its layout manager to decide where to put the component. -
Which arithmetic operations can result in the throwing of an ArithmeticException
Integer / and % can result in the throwing of an ArithmeticException.
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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.
Sandhya.Kishan
- Jul 14th, 2012
A thread can enter the waiting state by invoking wait() method, sleep() method and suspend() method.
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Can an abstract class be final
An abstract class may not be declared as final.
Sandhya.Kishan
- May 4th, 2012
Abstract classes are the classes which can be subclassed but once if a class is declared as final we cant sub class
that so that as abstract class can never be final. -
What is the ResourceBundle class
The ResourceBundle class is used to store locale-specific resources that can be loaded bya program to tailor the program's appearance to the particular locale in which it is beingrun.
Sandhya.Kishan
- Jun 14th, 2012
ResourceBundle is a set of related subclasses that share the same base name.It can be used instead of the Properties class. It is usefull when developing applications for different languages,the ResourceBundle class will find the correct properties file based on the current user locale.
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What is the difference between a Scrollbar and a ScrollPane
A Scrollbar is a Component, but not a Container. A ScrollPane is a Container. AScrollPane handles its own events and performs its own scrolling.
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What is the difference between a public and a non-public class
A public class may be accessed outside of its package. A non-public class may not beaccessed outside of its package.
Sandhya.Kishan
- Mar 31st, 2012
A public class will have access specifier "public" and its members can be accessed with in and out of the class in which they are specified. A class which doesnt have the public access specifier are c...
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To what value is a variable of the boolean type automatically initialized
The default value of the boolean type is false.
Sandhya.Kishan
- May 3rd, 2012
Boolean type variable is always automatically initialized to false value.
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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 incrementoperation. The postfix form returns the current value all of the expression and thenperforms the increment operation on that value.
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What is the purpose of a statement block
A statement block is used to organize a sequence of statements as a single statementgroup.
Sandhya.Kishan
- Mar 31st, 2012
Sequence of statements are organized as a single statement group with the help of statement block.
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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 isused to represent the classes and interfaces that are loaded by a Java program..
Sandhya.Kishan
- Jun 14th, 2012
Object class is the super class of all the classes in java.It defines methods which are inherited by all other classes.
Class class defines the behaviours and functionality for the classes in java.It also represent the classes and
interfaces that are loaded by a Java program.
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Can an unreachable object become reachable again
An unreachable object may become reachable again. This can happen when the object'sfinalize() method is invoked and the object performs an operation which causes it tobecome accessible to reachable objects.
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When is an object subject to garbage collection
An object is subject to garbage collection when it becomes unreachable to the program inwhich it is used.
Sandhya.Kishan
- May 3rd, 2012
When an object becomes unreachable to any of the code then that object becomes eligible for garbage collection.
Once an object is garbage collected, It can no longer become reachable again. -
What method must be implemented by all threads
All tasks must implement the run() method, whether they are a subclass of Thread orimplement the Runnable interface.
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