Lambda表达式

悠悠 2021-06-12 20:36 590阅读 0赞

Lambda表达式简单使用 ==>持续更新  
1.

/** 有两个LIst<Bean>, 比如Bean1中包含prjId,prjManagerName,prjStatus,Bean2中包含prjId,prjManagerName,prjStatus 求LIst1<Bean1>中prjId和List2<Bean2>中prjId相同的，并把Bean2中的prjManagerName,prjStatus赋给Bean1 */
    LIst1<Bean1> bean1List=new ArrayList<Bean1>();
    LIst1<Bean2> bean2List=new ArrayList<Bean2>();
     Map<String, List<Bean2>> stringListMap = bean2List.stream().collect(Collectors.groupingBy(bean2List::getPrjId));//把prjId分组
            bean1List.stream().forEach(e -> { 
                    //加你想加的判断
                Bean2 item = stringListMap.get(e.getPrjId()).get(0);
                e.setBean2(item);
     
            });

1.  List<Map.Entry<Integer,Double>> 进行倒序排序

//性价比数组
            Map<Integer,Double> price = new HashMap<>();  
            //将map的entryset放入list集合
            List<Map.Entry<Integer,Double>> list = new ArrayList<>(price.entrySet()); 
            //根据性价比排序并取出倒序序后下标
       		list.sort(Comparator.comparing(Map.Entry<Integer,Double>::getValue).reversed());

1.  取出两个list的交集

public static void main(String[] args) {
                List<Map<String, Object>> list1 = new ArrayList<>();
                Map<String, Object> item1 = new HashMap<>();
                item1.put("name", "张三");
                Map<String, Object> item2 = new HashMap<>();
                item2.put("name", "李四");
                Map<String, Object> item3 = new HashMap<>();
                item3.put("name", "王五");
                list1.add(item1);
                list1.add(item2);
                list1.add(item3);
                List<Map<String, Object>> list2 = new ArrayList<>();
                Map<String, Object> item4 = new HashMap<>();
                item4.put("name", "王五");
                list2.add(item4);
                //把名字取出当key
                Map<String, List<Map<String, Object>>> nameMap = list2.stream().collect(Collectors.groupingBy(e -> e.get("name").toString()));
                List<Map<String, Object>> list3 = new ArrayList<>();
                list1.stream().forEach(e -> {
                    if(!nameMap.containsKey(e.get("name").toString())){
                        return;
                    }
    
                    list3.add(e);
                });
                System.out.println(list3.toString());
    
        }