How to use Java static keyword

Description

A static class member can be used independently of any object of that class.

A static member that can be used by itself, without reference to a specific instance.

Syntax

Here shows how to declare static method and static variable.

/*from  w  w  w .j a v  a2s  .  co  m*/
static int intValue;

static void aStaticMethod(){
}

Restrictions

Methods declared as static have several restrictions:

• They can only call other static methods.
• They must only access static data.
• They cannot refer to this or super in any way.

All instances of the class share the same static variable. You can declare a static block to initialize your static variables. The static block gets only called once when the class is first loaded.

Example

The following example shows a class that has a static method

 
public class Main {
  static int a = 3;
  static int b;
//from w w  w .j a  v a2 s.co m
  static void meth(int x) {
    System.out.println("x = " + x);
    System.out.println("a = " + a);
    System.out.println("b = " + b);

  }

  public static void main(String args[]) {
    Main.meth(42);
  }
}

The output:

Example 2

The following example shows a class that has the static variables.

 
public class Main { 
    static int a = 3; 
    static int b; 
}

We can reference the static variables defined above as follows:

 
Main.a

Example 3

The following example shows a class that has a static initialization block.

 
public class Main {
//from w  w  w.  j av  a 2  s  . c  o  m
  static int a = 3;

  static int b;

  static {
    System.out.println("Static block initialized.");
    b = a * 4;
  }
}