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Which package is always imported by default
The java.lang package is always imported by default.
Sandhya.Kishan
- Jun 7th, 2012
The java,lang package is imported by default as it includes all other packages.
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What interface must an object implement before it can be written to a streamas an object
An object must implement the Serializable or Externalizable interface before it can bewritten to a stream asan object.
Sandhya.Kishan
- Jun 11th, 2012
Externalizable and serializable interfaces must be implemented by an object before it is written to the stream as an object.
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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 thesuperclass of the current object instance.
Sandhya.Kishan
- Jun 23rd, 2012
This() is used to refer the class scope variables. and method scope variables and it is used to invoke a constructor of the same class.
super() is used to refer super-class member and subclass member and it invoke a super-class constructor. -
What is the purpose of garbage collection
The purpose of garbage collection is to identify and discard objects that are no longerneeded by a programso that their resources may be reclaimed and reused.
Sandhya.Kishan
- Jun 15th, 2012
The purpose of garbage collection is to remove the unused variables/objects (value is null) from the memory,so that their resources can be reclaimed and reused by other programs.
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What is a compilation unit
A compilation unit is a Java source code file.
Sandhya.Kishan
- Jun 7th, 2012
The source code file 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.
Sandhya.Kishan
- May 22nd, 2012
Java.util.EventListener interface is extented by all AWT event listeners.
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How can a dead thread be restarted
A dead thread cannot be restarted.
Sandhya.Kishan
- May 19th, 2012
A thread once dead cannot be restarted. The thread is said to be dead only after it completes its execution with the expected results hence dead thread cannot be restarted.
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What happens if an exception is not caught
An uncaught exception results in the uncaughtException() method of the thread'sThreadGroup beinginvoked, which eventually results in the termination of the program in which it is thrown.
Sandhya.Kishan
- Jun 23rd, 2012
If the exception is not caught by any of the method in the methods stack , then the main method throws that exception and the JVM halts its execution.
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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 19th, 2012
Layout managers are software components which have the ability to lay out widgets by their relative positions without using distance units.It is an object that implements the LayoutManager interface* and determines the size and position of the components within a container.
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Which arithmetic operations can result in the throwing of anArithmeticException
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 unsuccessfullyattempting to acquire an object's lock, or by invoking an object's wait() method. It canalso enter thewaiting state by invoking its (deprecated) suspend() method.
Sandhya.Kishan
- Jun 15th, 2012
The thread can enter its waiting state by
1.invoking its sleep() method
2.By invoking its suspend() method
3.When an i/o block occurs. -
Can an abstract class be final
An abstract class may not be declared as final.
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What is the ResourceBundle class
The ResourceBundle class is used to store locale-specific resources that can be loaded bya program totailor the program's appearance to the particular locale in which it is being run.
Sandhya.Kishan
- Jun 15th, 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 useful when developing applications for different languages,the Resour...
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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 itsown events and performs its own scrolling.
Sandhya.Kishan
- May 24th, 2012
*A scroll-bar is a component. *A scroll bar provides a convenient means for allowing a user to select from a range of values. *Scroll-bars can either be vertical or horizontal. *It has multiples compo...
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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 ofits package.
Sandhya.Kishan
- Jul 31st, 2012
We can access a public class out of its package where as the access outside the package is not possible with a non public class.
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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 19th, 2012
A Boolean type is automatically initialized to value 0 or false value.
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Can try statements be nested
Try statements may be tested.
ashfaq02
- May 1st, 2008
Yes, try statements can be nested . first the inner statements will be executed .
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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
- May 19th, 2012
Statements that are of a sequence are organized as a single statement group with the help of statement block.
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What modifiers may be used with a top-level class
A top-level class may be public, abstract, or final.
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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 24th, 2012
When an object becomes unreachable to the program in which it is being used then an object subjects to the garbage collection.
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