Stream操作

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我是靠谱客的博主娇气水池，最近开发中收集的这篇文章主要介绍Stream操作，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

  Map<String,Object> map=new HashMap<>();
  map.put("name","李四");
  map.put("age","12");
  Map<String,Object> map1=new HashMap<>();
  map1.put("name","张三");
  map1.put("age","12");
  Map<String,Object> map2=new HashMap<>();
  map2.put("name","李四");
  map2.put("age","15");
  List<Map<String,Object>> list=new ArrayList<>();
  list.add(map1);
  list.add(map2);
  list.add(map);
  //对list<Map<String,Object>>去重
  list =  list.stream().collect(
          Collectors.collectingAndThen(
                  Collectors.toCollection(()->new TreeSet<>(Comparator.comparing(m->m.get("name").toString()))
                          ),ArrayList::new
          )
  );
  //对list<Object>去重
   List<Test> unique = list.stream().collect(
                Collectors.collectingAndThen(
                        Collectors.toCollection(() -> new TreeSet<>(Comparator.comparing(Test::getName))), ArrayList::new)
        );
  list.stream().forEach(item->{
      for (Map.Entry<String,Object> m:item.entrySet()){
          System.out.println(m.getKey()+":"+m.getValue());
      }
  });
  //map取出 key value
 Map<String,String> map = new HashMap<>();
        map.put("name","zhangsan");
        map.forEach((key, val) -> {
            System.out.println(key+":"+val);
        });
 //判断是否存在，存在返回true
boolean isBankGjdq = qbSsTjwjqkWqzbs.stream().filter(qbSsTjwjqkWqzb -> CommonResources.WQZB_SJSJ.getName().equals(qbSsTjwjqkWqzb.getJgmc())).findAny().isPresent();
//跳过指定个数的Stream中元素，获取后面的元素。
list.stream().skip(1).collect(Collectors.toList());
//取出某个字段的值
list.stream().map(user2 -> user2.getId()).collect(Collectors.toList());
//对指定字段求和
list.stream().collect(Collectors.summarizingInt(User::getAge));
//list转map
Map<Integer, User> map = list.stream().collect(Collectors.toMap(user2 -> user2.getId(), user2 -> user2));
//对Stream中的元素进行过滤操作，当设置条件返回true时返回相应元素。
list.stream().filter(uu -> uu.getAge() == 18).collect(Collectors.toList());