In an array list, new variable gets added and as well as replaces the existing values with new one

Question

In an array list, when new variables are added using

 pointList.add(i , coord); 

the new variable gets added and as well as replaces the existing values with new one. how to stop these replacing variables ?

for(int i=0;i<coordinateArray.length();i++)
        {
            brokenArray= coordinateArray.getJSONObject(i);  
            x=brokenArray.getInt("x");
            y=brokenArray.getInt("y");

            Log.d("x", " "+i+ " "+x );
            Log.d("y", " "+i+ " "+y );

            coord.set(x, y);
            pointList.add(i , coord);

            Log.d("pointList", pointList.toString());
        }

Answer 1

Based on the code you've provided, you're using coord.set(x, y) on the same object every time. Adding an object to a List does not make a copy of it.

Java passes references by value, not objects by value; when you call pointList.add(i, coord), you are adding a reference to the coord object to the list, not a new copy of the coord object.

Instead, you must create a new Point or Coordinates or whatever object each time through the loop. You cannot reuse the coord object the way you're doing it here.

Answer 2

This is the bug.

 coord.set(x, y);

You are setting the value in the loop to the same object.

Create the coord object inside the loop and add it.

for(int i=0;i<coordinateArray.length();i++)
    {
        brokenArray= coordinateArray.getJSONObject(i);  
        x=brokenArray.getInt("x");
        y=brokenArray.getInt("y");

        Log.d("x", " "+i+ " "+x );
        Log.d("y", " "+i+ " "+y );
        Coordinate coord = new Coordinate ();
        coord.set(x, y);

        pointList.add(i , coord);

        Log.d("pointList", pointList.toString());
    }