code: long get(final T key) {
      if (key == null) { return 0; }
      final int probe = hashProbe(key);
      if (states[probe] > 0) {
        assert (keys[probe]).equals(key);
        return values[probe];
      }
      return 0;
    }
docs: Gets the current value with the given key
  @param key the given key
  @return the positive value the key corresponds to or zero if the key is not found in the
  hash map.