static Weigher<Integer, Object> intKeyWeigher() {
    return new IntKeyWeigher();
  }

  /** Returns a {@link Weigher} that uses the integer value as the weight. */
  static Weigher<Object, Integer> intValueWeigher() {
    return new IntValueWeigher();
  }

  static final class ConstantWeigher implements Weigher<Object, Object> {
    private final int constant;

    ConstantWeigher(int constant) {
      this.constant = constant;
    }