Class as a DataType

Example creating object of a class:

public class Class_One {

       int xx = 5;

       public void methodA() {

             

              int yy=10;          

              System.out.println("This is inside Class_One.");

              System.out.println("This is value of yy = " +yy);

             

       }

      

       public static void main(String[] args) throws Exception {

             

              Class_One A = new Class_One();

              int aa = A.xx;

              System.out.println("aa = " +aa);

              A.methodA();

       }

      

}

Output:
aa = 5
This is inside Class_One.

This is value of yy = 10

Class as DataType:

public class Class_One {

       int xx = 5;

       public void methodA() {

              System.out.println("This is inside Class_One.");

       }

}

public class Class_Two {

       int i = 10;

       public void methodA(Class_One c) {

              System.out.println("This is inside Class_Two.");

              c.methodA();

              System.out.println("Value of xx from Class_One = " + c.xx);

       }

       public static void main(String[] args) throws Exception {

              Class_Two pc = new Class_Two();

              pc.methodA(new Class_One());

       }

}

Output:

This is inside Class_Two.

This is inside Class_One.

Value of xx from Class_One = 5

Above code can also be written as :

public class Class_One {

       int xx = 5;

       public void methodA() {

              System.out.println("This is inside Class_One.");

       }

}

public class Class_Two {

       int i = 10;

       public static void methodA(Class_One c) {  //added static

              System.out.println("This is inside Class_Two.");

              c.methodA();

              System.out.println("Value of xx from Class_One = " + c.xx);

       }

       public static void main(String[] args) throws Exception {

              methodA(new Class_One()); //removed object of the class two

       }

}

Output:

This is inside Class_Two.

This is inside Class_One.

Value of xx from Class_One = 5