code: @Override
      public V get(Object key) {
          if (fast) {
              return (map.get(key));
          } else {
              synchronized (map) {
                  return (map.get(key));
              }
          }
      }
docs: Return the value to which this map maps the specified key.  Returns
  <code>null</code> if the map contains no mapping for this key, or if
  there is a mapping with a value of <code>null</code>.  Use the
  <code>containsKey()</code> method to disambiguate these cases.
  
  @param key the key whose value is to be returned
  @return the value mapped to that key, or null