Java is call by value

A reference stored in a passed variable cannot be replaced with a different reference inside the method body.

This means that if a variable x stores a reference to an object ob, passing x into a method cannot cause x to point to a different object. The reference in x cannot be replaced with a different reference simply by passing x into a method. This is because when a variable x is passed, only a copy of x is passed, so pointing that copy to a different object (from within some method) will not affect x.

What is the output of the following code?

Example 1

public class CallByValue {
    int data = 50;
    int originalValue;
    void change(int data) {
        //this.data = data + 100 // change will be reflected in object
        data = data + 100;//changes will be in the local variable only
    }

    void callByValue(CallByValue copy){
//creates a new object
        copy = new CallByValue();  
        copy.originalValue = 2000;
    }
}

public class Main {
    public static void main(String args[]) {
        System.out.println("call by value in passing primitive value.......");
        CallByValue ob = new CallByValue();
        System.out.println("before change " + ob.data); //50
        ob.change(500); // passing a value
        System.out.println("after change " + ob.data); //50

        System.out.println("call by value in passing object reference.......");
        CallByValue ob1 = new CallByValue();
        ob1.originalValue = 1000;
        //sending a copy of reference but it is call by value
        ob1.callByValue(ob1); 
        // 1000 not 2000 since change in copy does not affect to the original value
        System.out.println("after change " + ob1.originalValue); //1000
    }
}

Example 2: use of "this" with call-by-value

public class JavaExample {
    int x = 10;
    int y = 20;
    void display(JavaExample A, JavaExample B){
        A.x = 95;
        B.y = 55;
        System.out.println("x = " + x);  
        System.out.println("y = " + y);
        //System.out.println("x = " + A.x); what happens?
        //System.out.println("x = " + A.x); what happens?
    }
    public static void main(String[] args) {
        JavaExample C= new JavaExample();
        JavaExample D = new JavaExample();
        D.y = 55;
        C.display(C, D); // x = 95, y = 20
        D.display(C, D); // x = 10, y = 55
    }
}