code: @SafeVarargs
  	@Pure
  	public static <K, V> HashMap<K, V> newHashMap(Pair<? extends K, ? extends V>... initial) {
  		if (initial.length > 0) {
  			HashMap<K, V> result = new HashMap<K, V>(capacity(initial.length));
  			putAll(result, initial);
  			return result;
  		}
  		return newHashMap();
  	}
docs: Creates a mutable {@link HashMap} instance containing the given initial entries. Repeated occurrences of a keys
  will cause an {@link IllegalArgumentException}.
  
  @param initial
  the entries that should be contained in the map. May not be <code>null</code> but may contain
  <code>null</code> keys or values.
  @return a new {@link HashMap} containing those elements
  @throws IllegalArgumentException
  if duplicate keys are contained the {@code initial} entries.