PASS BY VALUE AND PASS BY REFERENCE OR ADDRESS IN JAVA

In programming language we can call methods either by passing variables value or variable addresses. Calling a method by passing variable values is called pass by value and calling a method by passing variable address is called pass by address and there is no concept called pass by reference as per language designers.

Reference data type parameters, such as objects, are also passed into methods by value. This means, that when the method returns, the passed-in reference still refers the same object as before.

Example –

public class Method1 {

          int x;

          int y;

          void abc(Method1 e)

          {

                   System.out.println(e);

                   e=new Method1();

                   System.out.println(e);

          }

          public static void main(String[] args) {

                   Method1 m1 = new Method1();

                   Method1 m2 = new Method1();

                   System.out.println("m2: "+m2);

                   m1.abc(m2);

                   System.out.println("m2: "+m2);

          }

}

Output –

m2: method.Method1@15db9742

method.Method1@15db9742

method.Method1@6d06d69c

m2: method.Method1@15db9742

In the above program we have assigned new object to parameter variable. After that method execution, In main method m2 is still pointing to its own object. Since argument variable value is not changed when we change parameter value, this point proves that passing objects as argument also come under pass by value. However, the values of the object’s non-static variables can be changed in this method and those object modifications are effected to passed-in reference variable, because both passed-in reference variable and method point parameter point to the same object.