code: public Xmap<K, V> xputAll(Map<K, V> map) {
          putAll(map);
          return this;
      }
docs: The same as {@link java.util.Map#putAll(Map) java.util.Map.putAll(map)}.<br>
  The only difference is that this method returns 'this'. In this way, we can easily use chained calls.
  <p>
  eg. <code>Xmap xmap = Xmap.create().xputAll(map).xput("cat","Tom").xput("mouse","Jerry");</code>
  </p>
  
  @return this xmap.