static LookupImpl toLookup_()

in src/main/java/net/hydromatic/linq4j/EnumerableDefaults.java [1928:1956]

• 27 lines of code
• 4 McCabe index (conditional complexity)

  static <TSource, TKey, TElement> LookupImpl<TKey, TElement> toLookup_(
      Map<TKey, List<TElement>> map, Enumerable<TSource> source,
      Function1<TSource, TKey> keySelector,
      Function1<TSource, TElement> elementSelector) {
    final Enumerator<TSource> os = source.enumerator();
    try {
      while (os.moveNext()) {
        TSource o = os.current();
        final TKey key = keySelector.apply(o);
        List<TElement> list = map.get(key);
        if (list == null) {
          // for first entry, use a singleton list to save space
          list = Collections.singletonList(elementSelector.apply(o));
        } else {
          if (list.size() == 1) {
            // when we go from 1 to 2 elements, switch to array list
            TElement element = list.get(0);
            list = new ArrayList<TElement>();
            list.add(element);
          }
          list.add(elementSelector.apply(o));
        }
        map.put(key, list);
      }
    } finally {
      os.close();
    }
    return new LookupImpl<TKey, TElement>(map);
  }