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Core Java Interview Question Page 8

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Question: What are the static fields & static Methods ? Answer: If a field or method defined as a static, there is only one copy for entire class, rather than one copy for each instance of class. static method cannot accecss non-static field or call n

Core Java Interview Question Page 8

     

Question: What are the static fields & static Methods ? 

Answer: If a field or method defined as a static, there is only one copy for entire class, rather than one copy for each instance of class. static method cannot accecss non-static field or call non-static method

Example Java Code

static int counter = 0;

A public static field or method can be accessed from outside the class using either the usual notation:

Java-class-object.field-or-method-name

or using the class name instead of the name of the class object:

Java- class-name.field-or-method-name

Question: What are the Final fields & Final Methods ? 

Answer: Fields and methods can also be declared final. A final method cannot be overridden in a subclass. A final field is like a constant: once it has been given a value, it cannot be assigned to again.

Java Code

private static final int MAXATTEMPTS = 10;

Question: Describe the wrapper classes in Java ? 

Answer: Wrapper class is wrapper around a primitive data type. An instance of a wrapper class contains, or wraps, a primitive value of the corresponding type.

Following table lists the primitive types and the corresponding wrapper classes:

Primitive

Wrapper

boolean

java.lang.Boolean

byte

java.lang.Byte

char

java.lang.Character

double

java.lang.Double

float

java.lang.Float

int

java.lang.Integer

long

java.lang.Long

short

java.lang.Short

void

java.lang.Void

Question: What are different types of inner classes ? 

Answer: Inner classes nest within other classes. A normal class is a direct member of a package. Inner classes, which became available with Java 1.1, are four types

  • Static member classes
  • Member classes
  • Local classes
  • Anonymous classes

Static member classes - a static member class is a static member of a class. Like any other static method, a static member class has access to all static methods of the parent, or top-level, class.

Member Classes - a member class is also defined as a member of a class. Unlike the static variety, the member class is instance specific and has access to any and all methods and members, even the parent's this reference.

Local Classes - Local Classes declared within a block of code and these classes are visible only within the block.

Anonymous Classes - These type of classes does not have any name and its like a local class

Java Anonymous Class Example public class SomeGUI extends JFrame { ... button member declarations ... protected void buildGUI() { button1 = new JButton(); button2 = new JButton(); ... button1.addActionListener( new java.awt.event.ActionListener() <------ Anonymous Class { public void actionPerformed(java.awt.event.ActionEvent e) { // do something } } );
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Posted on: March 27, 2008

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Comments:1
vidhya
August 16, 2011
java

hi please send all java jsp servlets and struts interview question to my mail for taking printout
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