java8- circulation and filtering case

• forEach

  jsonArray.stream().forEach(jsonObject->{
          JSONObject o = (JSONObject) jsonObject;
          //todo 操作对象 o
      });
  

• filter
  • After filtration generates a new set of set

  List<SysDictData> DictList = list.stream()
                 .filter(a -> goods.getGoodsUnit().equals(a.getDictLabel()))
                 .collect(Collectors.toList());
  

  • List deduplication

  List<GoodsSkuHistory> list = skuHistories.stream()
  			.filter(distinctByKey(o->o.getGoodsSkuId())).collect(Collectors.toList());
  /**
   * 去重使用
   * @param keyExtractor
   * @param <T>
   * @return
   */
  public static <T> Predicate<T> distinctByKey(Function<? super T, Object> keyExtractor) {
      Map<Object, Boolean> seen = new ConcurrentHashMap<>();
  	return t -> seen.putIfAbsent(keyExtractor.apply(t), Boolean.TRUE) == null;
  }