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 members are common for all the instances(objects) of the class but non-static members are separate for each instance of class.
class SimpleStaticExample
{
    static void myMethod()
    {
        System.out.println("myMethod");
    }
 
    public static void main(String[] args)
    {
          /* You can see that we are calling this
           * method without creating any object. 
           */
           myMethod();
    }
}
Output:- 
myMethod

Static Block

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.

Example 1: Single static block

As you can see that both the static variables were initialized before we accessed them in the main method.
class JavaExample{
   static int num;
   static String mystr;
   static{
      num = 97;
      mystr = "Static keyword in Java";
   }
   public static void main(String args[])
   {
      System.out.println("Value of num: "+num);
      System.out.println("Value of mystr: "+mystr);
   }
}
Output:
Value of num: 97
Value of mystr: Static keyword in Java

Java Static Variables

A static variable is common to all the instances (or objects) of the class because it is a class level variable. In other words you can say that only a single copy of static variable is created and shared among all the instances of the class. Memory allocation for such variables only happens once when the class is loaded in the memory. Few Important Points:
  • Static variables are also known as Class Variables.
  • Unlike non-static variables, such variables can be accessed directly in static and non-static methods.

Example 1: Static variables can be accessed directly in Static method

Here we have a static method disp() and two static variables var1 and var2. Both the variables are accessed directly in the static method.
class JavaExample3{
  static int var1;
  static String var2;
  //This is a Static Method
  static void disp(){
      System.out.println("Var1 is: "+var1);
      System.out.println("Var2 is: "+var2);
  }
  public static void main(String args[]) 
  {
      disp();
  }
}
Output:
Var1 is: 0
Var2 is: null

Java 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. Syntax: Static keyword followed by return type, followed by method name.
static return_type method_name();

Example 1: static method main is accessing static variables without object

class JavaExample{
   static int i = 10;
   static String s = "studywithbs";   //This is a static method
   public static void main(String args[]) 
   {
       System.out.println("i:"+i);
       System.out.println("s:"+s);
   }
}
Output:
i:10
s:studywithbs

Static Class

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
We will see these two points with the help of an example:

Static class Example

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

   //Static class
   static class MyNestedClass{
 //non-static method
 public void disp() {  
    System.out.println(str); 
 }

   }
   public static void main(String args[])
   {
 JavaExample.MyNestedClass obj = new JavaExample.MyNestedClass();
 obj.disp();
   }
}
Output:
studywithbs