Static Keyword : Introduction

• There will be time when you want a class member to be common to all the object of the class, i.e. all the objects of the class will share that member.
• Here static keyword comes into play.
• To access any member of the class it is done by using object with (.) operator.
• But static keyword before any class member makes it independent of the object.

Static Keyword : The Discussion

• Static keyword can be applied to:
  • Variable
  • Method
  • Block
• Let us discuss them one by one along with their respective syntax and examples.

1. Static variable

   • A variable preceded with static keyword is called static variable. Static variable is common to all class objects.
   • Static variable is independent of the objects hence is accessed using class name rather then object name.
   
   Syntax

   class_name.static_variable;

   
   
   Static Variable
   • The above diagram show that static variable a is common to all objects of a class.
   
   
   Static Variable : Example
   
   Static Variable : Output
   • As we can see that value of static variable is common to all objects and it is not reinitialized again to "0" when accessed again.
    

2. Static Methods

   • The most common example of static method we have seen till now is the main() method.
   • Static methods are those methods which are made static by preceding them with static keyword. Static methods access static data only.
   • Static methods are invoked using class name rather than object name.
   
   Syntax

   class_name.method_name();

    
   • There are some restrictions that are applied to static methods, such as :
     1. Static methods always access static data. They can’t access non-static data.
     2. This keyword cannot be used with static method.
     3. Super keyword cannot be used with static method.
   • Let us take an example of static method.
   
   
   Static Method : Example
   
   Static Method : Output  

3. Static Block

   • Static block is used to initialize static variables. Static block is always executed before main block.
   • Let us take an example of static block and see if it executes before main block.
   
   
   Static Block : Example
   
   Static Block : Output
   • We can see in the output that the static block is executed before main block and the static variable a is assigned value before main() starts executing.