java - How to use two numbers as a Map key

Question

I have two numbers and I want to use them together as a key in a Map. Currently, I'm concatenating their string representations. For example, suppose the key numbers are 4 and 12. I use:

String key = 4 + "," + 12;

The map is declared as Map<String, Object>.

I think this is so bad! I like to use something other than a String as the key! I want the fastest way to create these keys.

Who has a good idea?

Answer 1

Create an object that holds the two numbers and use it as the key. For example:

class Coordinates {

  private int x;
  private int y;

  public Coordinates(int x, int y) {
     ...
  }

  // getters

  // equals and hashcode using x and y
}

Map<Coordinates, Location> locations = new HashMap<Coordinates, Location>();

If you prefer a mathematical approach, see this StackOverflow answer.