Java map with values limited by key’s type parameter

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You’re not trying to implement Joshua Bloch’s typesafe hetereogeneous container pattern are you? Basically:

public class Favorites {
  private Map<Class<?>, Object> favorites =
    new HashMap<Class<?>, Object>();

  public <T> void setFavorite(Class<T> klass, T thing) {
    favorites.put(klass, thing);
  }

  public <T> T getFavorite(Class<T> klass) {
    return klass.cast(favorites.get(klass));
  }

  public static void main(String[] args) {
    Favorites f = new Favorites();
    f.setFavorite(String.class, "Java");
    f.setFavorite(Integer.class, 0xcafebabe);
    String s = f.getFavorite(String.class);
    int i = f.getFavorite(Integer.class);
  }
}

From Effective Java (2nd edition) and this presentation.

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