java8 流式写法那些事

Posted 2021-06-23 大树叶

Java8有好多新的写法，眼花缭乱，如下：

Stream写法

例子1：

Java以前的写法 

   List<Long> recordsIDlist = new ArrayList<>(retrecordsList.size());
   retrecordsList.forEach(item -> {recordsIDlist.add(item.getRecordId());});
            

Java8 新写法

List<Long> recordsIDlist=
retrecordsList.stream().map(DiffStatementsSnapshot::getRecordId).collect(Collectors.toList());

或者为：

  List<Long> recordsIDlist= retrecordsList.stream().map(item -> item.getRecordId()).collect(Collectors.toList());

ofNullable用法 

   return Optional.ofNullable(OFFSET_CACHE.get(coupleInfo.getCoupleId())).map(WeakReference::get).orElseGet(() -> {
            OffsetCondition offsetCondition = JSON.parseObject(coupleInfo.getOffsetCondition(), OffsetCondition.class);
            OFFSET_CACHE.put(coupleInfo.getCoupleId(), new WeakReference<>(offsetCondition));
            return offsetCondition;
        });

 

参考文档：

1. https://blog.csdn.net/qq_38360675/article/details/103089167

2.https://blog.csdn.net/zjhred/article/details/84976734

3.https://www.jb51.cc/java/123008.html

4. 集合工具类CollectionUtils、ListUtils、SetUtils、MapUtils的使用