Java – Static Class, Block, Methods and Variables

Cited from Java – Static Class, Block, Methods and Variables

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Static keyword can be used with class, variable, method and block. Static members belong to the class instead of a specific instance, this means if you make a member static, you can access it without object. Let’s take an example to understand this:

Here we have a static method myMethod(), we can call this method without any object because when we make a member static it becomes class level. If we remove the static keyword and make it non-static then we must need to create an object of the class in order to call it.

Static block is used for initializing the static variables.This block gets executed when the class is loaded in the memory. A class can have multiple Static blocks, which will execute in the same sequence in which they have been written into the program.

• Static variables are also known as Class Variables.
• Unlike non-static variables, such variables can be accessed directly in static and non-static methods.

Static Methods can access class variables(static variables) without using object(instance) of the class, however non-static methods and non-static variables can only be accessed using objects.
Static methods can be accessed directly in static and non-static methods.

A class can be made static only if it is a nested class.

1. Nested static class doesn’t need reference of Outer class
2. A static class cannot access non-static members of the Outer class

class JavaExample{
   private static String str = "BeginnersBook";

   //Static class
   static class MyNestedClass{
 //non-static method
 public void disp() {

    /* If you make the str variable of outer class
     * non-static then you will get compilation error
     * because: a nested static class cannot access non-
     * static members of the outer class.
     */
    System.out.println(str); 
 }

   }
   public static void main(String args[])
   {
       /* To create instance of nested class we didn't need the outer
 * class instance but for a regular nested class you would need 
 * to create an instance of outer class first
        */
 JavaExample.MyNestedClass obj = new JavaExample.MyNestedClass();
 obj.disp();
   }
}

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