Java static nested class

Static Nested Class in Java : Nested Class

Consider the following example of the static nested class -

package com.c4learn.nestedclss;
class OuterClass {
    private static int serialNo = 10;
    static class InnerClass {
	int getValue() {
	   return serialNo;
	}
    }
}
public class StaticNestedClassExample {
   public static void main(String[] args) {
     OuterClass.InnerClass m1 = new OuterClass.InnerClass();
     System.out.println("Sr. Number :" + m1.getValue());
   }
}

Explanation :

1. We can refer the nested class using the following syntax -

OuterClassName.InnerClassName

2. You have access to the outer class static members from inside your static nested class. Consider the following Static Nested Class -

class OuterClass {
   private static int serialNo = 10;
   private int panNo  = 10;
   public  int rollNo = 20;
   static class InnerClass {
     int getValue() {
	return serialNo;
     }
   }
}

3. No need to create an instance of the enclosing class to instantiate a static nested class.

OuterClass outObj = new OuterClass();

There is no need to create instance of the Outer Class in order to access Inner Static Class

What would happen if Same Variable is declared inside Inner Class ?

If you declare a member in a nested class that has the same name as a member in the Outer class then Inner member will shadow Outer Class member -

package com.c4learn.nestedclss;
class OuterClass {
   private static int serialNo = 10;
   static class InnerClass {
      int serialNo = 20;
      int getValue() {
	 return serialNo;
      }
   }
}
public class StaticNestedClassExample {
   public static void main(String[] args) {
      OuterClass.InnerClass m1 = new OuterClass.InnerClass();
      System.out.println("Sr. Number :" + m1.getValue());
   }
}

Output :

Sr. Number : 20