code: public <M extends Map<K, V>> M into(M map) {
          Consumer<? super Entry<K, V>> cons = toMapConsumer(map);
          if (isParallel()) {
              if (map instanceof ConcurrentMap)
                  forEach(cons);
              else
                  toMap().entrySet().forEach(cons);
          } else {
              spliterator().forEachRemaining(cons);
          }
          return map;
      }
docs: Drains the stream content into the supplied {@code Map}.
  
  <p>
  This is a <a href="package-summary.html#StreamOps">terminal</a>
  operation.
  
  @param <M> type of the resulting map
  @param map a mutable map to put the stream elements into
  @return the supplied map, updated from this stream
  @throws IllegalStateException if this stream contains duplicate keys, or
  the stream contains the key which was already present in the map
  (according to {@link Object#equals(Object)})
  @since 0.6.3