I can access private variables in Java

Question

someObj.java

public class someObj {
        private int data;

        someObj(int initVal) {
            data = initVal;
        }
        int getAnotherObjectData(someObj bar) {
            return bar.data;
        } 
}

Tester.java

    someObj foo = new someObj(30);
    someObj bar = new someObj(40);
    System.out.println(bar.getAnotherObjectData(foo));

In result, I can get '30'. Why I can access another Object's private variable data?

If a variable is private, it means you can't access it outside the class where it's declared. It doesn't mean that you can't access it from another object of the same class. — Dawood ibn Kareem, May 31 '15 at 03:26
More specific duplicate: http://stackoverflow.com/q/17027139 — Dan Getz, May 31 '15 at 03:31

score 2 · Accepted Answer · answered May 31 '15 at 03:29

As it's the same class implementation, it means that you are writing this class by yourself, so you can control it 100%. So it's not a problem if you can access other objects of the same type as well. Such feature can be useful when implementing equals or clone methods like this:

public class MyObj {
    private int a;
    private long b;

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        MyObj other = (MyObj) obj;
        if (a != other.a)
            return false;
        if (b != other.b)
            return false;
        return true;
    }
}

Without field access for proper equals implementation you would need to have non-private getters for all fields which may be not desired in many cases.

I can access private variables in Java

Tester.java

1 Answers1