Why are these variables not loading in ArrayList

Question

I cannot find whats wrong with this code. I have short type array called "data". I assign data[i] value to private Point objects variable x then I add this object to ArrayList and proceed with next i. In the arraylist all instances have same value - last one that was added. Why do you think its so?

    ArrayList<Point> p = new ArrayList<Point>();

        System.out.println("start test");
    for (int i=0;i<data.length;i++){

        bPunkt.x=(int) data[i];
        p.add(bPunkt);
        System.out.println(""+bPunkt.x);
    }
        System.out.println("middle of test");
    for (int i=0;i<p.size();i++){
        System.out.println(""+p.get(i).x);
    }
        System.out.println("end test");

this is what system.out prints :

start test
1
0
1
3
3
5
3
5
5
4
middle of test
4
4
4
4
4
4
4
4
4
4
end test

You need to assign a new instance to bPunkt before adding. — Bhesh Gurung
– Bhesh Gurung, Commented Mar 8, 2014 at 22:09

Giovanni Botta · Accepted Answer · 2014-03-08 22:10:35Z

2

You are modifying the same instance bPunkt and sticking it in the list. So in the end you have a list with the same object over and over in it.

answered Mar 8, 2014 at 22:10

Giovanni Botta

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3 Comments

Farhan Syed Over a year ago

Next time you feel stuck with such issues, print object references. It really helps.

Giovanni Botta Over a year ago

You can only do that if you do not override toString().

Giovanni Botta Over a year ago

Actually I stand corrected.

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