Change in value via object reference not changing in java? please refer below code

Question

class Demo {

    public static void main(String args[]) {
        A a = new A();
        A b = a;
        System.out.println(a.x);// 10 As expected
        System.out.println(b.x);// 10 As expected
        a.change();
        System.out.println(a.x);// 10 WHY 10! still. Displays 20 if I remove int
                                // data type under change method.
        System.out.println(b.x);// 10 WHY 10! still.Displays 20 if I remove int
                                // data type under change method.

    }

}

class A {

    int x = 10;

    public void change() {
        int x = 20; // I am delcaring this with int data type
    }

}

`int x = 20;` inside method, create a new local variable with name x. — Subhrajyoti Majumder, Sep 03 '15 at 08:22
@SubhrajyotiMajumder `create a new local variable` ? That is actually causing the issue :) — Suresh Atta, Sep 03 '15 at 08:23
Read about [variables](https://docs.oracle.com/javase/tutorial/java/nutsandbolts/variables.html) in java. — alex2410, Sep 03 '15 at 08:35
possible duplicate of [Is Java "pass-by-reference" or "pass-by-value"?](http://stackoverflow.com/questions/40480/is-java-pass-by-reference-or-pass-by-value) — merours, Sep 03 '15 at 08:37
I got it as Creating local variable wil be inside the local scope to that method only, it wil not over ride the instance variable... — Pradeep kumar, Sep 03 '15 at 12:14

score 2 · Accepted Answer · edited Sep 03 '15 at 08:23

2

In the method

public void change(){
    int x=20; // I am declaring this with int data type
}

You are declaring a new variable which is not the variable x at instance level.

Change your method to

public void change(){
    this.x=20; // I am declaring this with int data type
}

edited Sep 03 '15 at 08:23

Scott

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answered Sep 03 '15 at 08:20

Suresh Atta

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Change in value via object reference not changing in java? please refer below code

1 Answers1