利用Lambda处理集合常用方法

Map userMap = list.stream().collect(Collectors.toMap(User::getName, a -> a,(k1, k2)->k1));
        System.out.println(userMap);

        User user=new User();
        user.setName("good");
        user.setAddr("dd");
        User user2=new User();
        user2.setName("goodbye");
        user2.setAddr("dda");
        List list=new ArrayList<>();
        list.add(user);
        list.add(user2);
        list.stream().forEach(userObj->{
            System.out.println(userObj.getName());
        });

Map> groupBy = list.stream().collect(Collectors.groupingBy(User::getName));
        System.out.println(groupBy);

List filterList = list.stream().filter(user3 -> user3.getName().equals("good")).collect(Collectors.toList());
        filterList.stream().forEach(user3 ->{
            System.out.println(user3.getName());
        });

Map userMap2 = list.stream().collect(Collectors.toMap(User::getName, User::getAddr,(k1, k2)->k1));
        System.out.println(userMap2);