code: @SuppressWarnings("unchecked")
      public static final <K,V> Map<K,V> emptyMap() {
          return (Map<K,V>) EMPTY_MAP;
      }
docs: Returns an empty map (immutable).  This map is serializable.
  
  <p>This example illustrates the type-safe way to obtain an empty map:
  <pre>
  Map&lt;String, Date&gt; s = Collections.emptyMap();
  </pre>
  @implNote Implementations of this method need not create a separate
  {@code Map} object for each call.  Using this method is likely to have
  comparable cost to using the like-named field.  (Unlike this method, the
  field does not provide type safety.)
  
  @param <K> the class of the map keys
  @param <V> the class of the map values
  @return an empty map
  @see #EMPTY_MAP
  @since 1.5