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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 listof available choices. Only one item may be selected from a Choice. A List may bedisplayed in such a way that several List items are visible. A List supports the selectionof one or more List items.
Sandhya.Kishan
- Apr 3rd, 2012
Choice is an action of choosing or selection,it requires us to pull it down to see the list of available choices.Only one item can be choosen from the list of choices.
Several list items are visible in a list and more then one item can be selected using list. -
What class of exceptions are generated by the Java run-time system
The Java runtime system generates RuntimeException and Error exceptions.
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What class allows you to read objects directly from a stream
The ObjectInputStream class supports the reading of objects from input streams.
Sandhya.Kishan
- Apr 3rd, 2012
The ObjectInputStream class supports to read object directly from stream.
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Under what conditions is an object's finalize() method invoked by the garbagecollector
The garbage collector invokes an object's finalize() method when it detects that the objecthas become unreachable.
Sandhya.Kishan
- May 7th, 2012
When an object becomes unreachable by any of the methods in a program then the finalize() method in invoked.
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How are this() and super() used with constructors
This() is used to invoke a constructor of the same class. super() is used to invoke asuperclass constructor.
vegetto
- Jun 15th, 2008
this() is used to specify the current class or the child's class constructor alwaysand super() refers to the parent's class constructorTo use them follw the rules:super()has to be the first li...
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What Checkbox method allows you to tell if a Checkbox is checked
getState()
Sandhya.Kishan
- May 7th, 2012
The method which is used to check whether the checkbox is checked or not is the getstate() method.
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What state is a thread in when it is executing
An executing thread is in the running state.
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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 agrid.
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What an I/O filter
An I/O filter is an object that reads from one stream and writes to another, usuallyaltering the data in some way as it is passed from one stream to another.
Sandhya.Kishan
- Apr 3rd, 2012
An object which is used to read from one stream and write those on other stream is known as an i/o filter.
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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 reachableagain.
Sandhya.Kishan
- May 7th, 2012
An object reaches the garbage collector as it becomes unreachable ,hence once an object is garbage collected it cannot be made reachable again.
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What is the Set interface
The Set interface provides methods for accessing the elements of a finite mathematicalset. Sets do not allow duplicate elements.
Sandhya.Kishan
- Apr 3rd, 2012
The Set interface contains only methods that are inherited from a Collection interface and does not allow the addition of duplicate elements.Two Set instances are equal if they contain the same elements.
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What classes of exceptions may be thrown by a throw statement
A throw statement may throw any expression that may be assigned to the Throwabletype.
Sandhya.Kishan
- Jul 24th, 2012
Exceptions which are assigned Throwable Type are thrown by a throw statement.
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What are E and PI
E is the base of the natural logarithm and PI is mathematical value pi.
Sandhya.Kishan
- Apr 3rd, 2012
"e" is a numerical constant that is equal to 2.71828.The value of "e" is found in many mathematical formulas such as those describing a nonlinear increase or decrease such as growth or decay."e" is us...
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What is a void return type
A void return type indicates that a method does not return a value.
Sandhya.Kishan
- May 7th, 2012
Void return type specifies that the particular function will not return any value.
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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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