JAVA #23 – Nested Classes and Static Keyword in Java

Nested Classes in Java

The Java programming language allows you to define a class within another class. Such a class is called a nested class

Nested classes are divided into two categories: static and non-static. Nested classes that are declared static are called static nested classes. Non-static nested classes are called inner classes.

Syntax:

public class Test {

   public void class1() {
        . . .
   }
   public void class2() {
        .. .
   }
}
public class Testing {
   public static void main(String[] args) {
        . . .
   }
}

// File name NestedClasses.java 
package nestedclasses;
public class NestedClasses {
    public static void main(String[] args) {
        Testing T = new Testing(); // Outter Class
        Testing.Test1 T1 = T.new Test1(); // Nested Object Of An Class
        T1.Dis();
        
        Testing.Test2 T2 = new Testing.Test2();
        T2.Dis();
        
        int a = Testing.i;
        System.out.println(a);
        Testing.Display("Ali");
    }
}

// File name Testing.java must be store in same package of above class.
package nestedclasses;
public class Testing {    
    public static void Display(String name)
    {
        System.out.println("The Name Is: "+name);
    }   
    public static int i = 10;
        public class Test1{
             public void Dis()
            {
                System.out.println("Test1 Class");
            }
        }       
        public static class Test2{
             public void Dis()
            {
                System.out.println("Test2 Class");
            }
       }
}