Java static keyword

In this chapter you will learn:

1. How to declare a static method and use it
2. Syntax for static keyword
3. Restrictions for Java static keyword
4. Example - static methods
5. Example - static variables
6. How to use static initialization block

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   ww  w.  j a  v  a  2 s.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 .  ja va 2  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 {
/*  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;
  }
}

Next chapter...

What you will learn in the next chapter:

1. What is method overloading
2. Note for Java Method Overload
3. Example - How to overload methods with different parameters
4. Example - How does automatic type conversions apply to overloading

Java static keyword