code: @SuppressWarnings("unchecked")
      public void putAll(Map t) {
          // don't delegate to putAll since we want case handling from put
          for (Entry next : (Set<Entry>) t.entrySet()) {
              put(next.getKey(), next.getValue());
          }
      }
docs: Copies all of the mappings from the specified map to this result.
  If the map contains different case versions of the same (case-insensitive) key
  only the last (according to the natural ordering of the supplied map) will remain
  after the {@code putAll} method has returned.
  
  @param t the mappings to store in this result