Question

I’ve got some legacy code that I want to upgrade to generics:

    /**
     * Places in this World
     */
  public Map places;

    /**
     * Players watching this World
     */ 
  public Collection players;

    /**
     * A reference to the Adventure using this World
     */
  public Adventure owner;

    /**
     * Create a World.  `a' is a reference to the Frame itself.
     * This reference is used when loading images and sounds.
     *
     * @param a An instance of adventure.
     */
  public World( Adventure a ) {
    places = new HashMap();
    players = new LinkedList();
    owner = a; 
  }

My IDE warns me that I have not parametrized the variables places and players so I should add generics to this code but how? When I add <> or <Place> to the `places´ object then it says it is not generics so however I do it turns out wrong. Could you tell me how to modernize this part of my code to using generics?

Thanks

Answer 1

As for places…

First, add types to places. Assuming each value is a Place, and each key is a String:

public Map<String, Place> places;

(You need two types: one for the keys, and one for the values.)

Then, in your constructor, do the same thing.

Like so:

public World(Adventure a) {
    places = new HashMap<String, Place>();
    ...
}

The other fields are simpler; LinkedList and Collection should only require one type, and if this is old old code, Adventure (being part of that code) wouldn’t need any.