Static Keyword

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Static Keyword

Is used to define class members.
In a class we can have following 3 types of class members:-

1. STATIC DATA MEMBERS
2. STATIC INITIALIZE BLOCK
3. STATIC METHODS.

(1) STATIC DATA MEMBERS

Represents class attributes. A single copy of static data members is created when the class is loaded. This copy can be shared by all the objects of the class.

For example -

2. class A
3. {
4. int a, b;
5. static int c;
6. -------
7.         -------
8. }

When we create objects of this class in some other class what happens is explained in the given adjoining fig1.

Fig1.

For the execution of a Java Application, memory is divided into three parts called

·      Stack - LOCAL VARIABLES of methods are stored in STACK.

·     Heap - OBJECTS are created in the HEAP.

·     Class Area - STATIC DATA MEMBERS are saved in CLASS AREA.

(2) STATIC INITIALIZE BLOCK

(3) STATIC METHODS.

1. class A
   {
                  int a, b;
                  static int c;
                  ----------              
                  ----------
                  public static void main(String[] args)
                  {
                                 A x = new A();
                                 A y = new A();
                                 -------------
   -------------
                  }
   }
2. 
   

Memory Representation During the execution of main() method of class A.

Static Initializer Block- is used to initialize static data members of a class.

Syntax –

static

{

         Statements

} 

Static initialize is executed only once, just after a class is loaded.
In Java, a class can be loaded in either of the following ways:-

(1). Through Explicit Introduction.
(2). Through Implicit References.

In the first approach class to be loaded is explicitly introduced to the JRE.

Only a single class is loaded in an application using explicit introduction. Rests of the classes are loaded through implicit reference.
When a reference of a class is encountered first time in an already loaded class then JRE implicitly loads it before performing the operation represented by the class reference.

2. class A
3. {
4. public static void main(String[ ] args)
5. {
6. B x = new B();//Reference of B is contained in A
7. -------------
8. -------------
9. }
10. }
11. 
    
12. class B
13. {
14.  -------------
15.  -------------
16. }

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