Question

Given an object we will call loc that simply holds 2 int member values, I believe I need to come up with a mechanism to generate a hashcode for the object. What I tried below doesn’t work as it uses an object reference, and the 2 references will be different despite having the same members variables.

Map<Loc,String> mapTest = new HashMap<Loc,String>();
        mapTest.put(new Loc(1,2), "String 1");
        mapTest.put(new Loc(0,1), "String 2");
        mapTest.put(new Loc(2,2), "String 3");

        System.out.println("Should be String 2 " + mapTest.get(new Loc(0,1)));

After some reading it seems I need to roll my own hashcode for this object, and use that hashcode as the key. Just wanted to confirm that I am on the right track here, and if someone could guide me to simple implementations to look at that would be excellent.

Thanks

Answer 1

Yes, you’re on the right track.

See articles like this for more details.

There are a lot of different ways to implement a hashcode, you’ll probably just want to combine the hashcodes of each integer primitive.