code: public static <K, V> HashMap<K, V> constrainedHashMap(final int s) {
          return new HashMap<K, V>(s, 1.0F);
      }
docs: Returns a hash map of type {@code K, V} optimized to trade memory
  efficiency for CPU time.
  <p>
  Use constrained hash maps when the capacity of a hash map is known to be
  greater than sixteen (the default initial capacity) and the addition of
  elements beyond the map's capacity will not occur. The hash map
  implementation will automatically adjust the size to the next nearest
  power of two.
  </p>
  
  @param <K> Formal type parameter key
  @param <V> Formal type parameter value
  @param s Initial hash map capacity
  @return Hash map of type {@code K, V}