Java static nested class

A static class is a class that is created inside a class, is called a static nested class in Java. It cannot access non-static data members and methods. It can be accessed by outer class name.

It can access static data members of the outer class, including private.
The static nested class cannot access non-static (instance) data members or

Java static nested class example with instance method

TestOuter1.java

class TestOuter1{
  static int data=30;
  static class Inner{
   void msg(){System.out.println("data is "+data);}
  }
  public static void main(String args[]){
  TestOuter1.Inner obj=new TestOuter1.Inner();
  obj.msg();
  }
}

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Output:

data is 30

In this example, you need to create the instance of static nested class because it has instance method msg(). But you don't need to create the object of the Outer class because the nested class is static and static properties, methods, or classes can be accessed without an object.

Internal class generated by the compiler

import java.io.PrintStream;
static class TestOuter1$Inner
{
TestOuter1$Inner(){}
void msg(){
System.out.println((new StringBuilder()).append("data is ")
.append(TestOuter1.data).toString());
}  
}

Java static nested class example with a static method

If you have the static member inside the static nested class, you don't need to create an instance of the static nested class.

TestOuter2.java

public class TestOuter2{
  static int data=30;
  static class Inner{
   static void msg(){System.out.println("data is "+data);}
  }
  public static void main(String args[]){
  TestOuter2.Inner.msg();//no need to create the instance of static nested class
  }
}

Test it Now

Output: