List转Map

stream List转Map

 List<User> list = new ArrayList();
        list.add(new User("1001", "18", "张三"));
        list.add(new User("1002", "22", "李四"));
        list.add(new User("1003", "23", "王五"));
        System.out.println(list);

        //将list转换map1, key id  value name
        Map<String, String> map1 = list.stream().collect(Collectors.toMap(User::getId, User::getName,(key1,key2)->key1));
        System.out.println("map1, Id作为key: "+map1);

        //将list转换map2, key id+name  value entity
        Map<String, User> map2 = list.stream().collect(Collectors.toMap(
                new Function<User, String>() {
                    @Override
                    public String apply(User user) {
                        return user.getId() + user.getName();
                    }},
                Function.identity(),(key1,key2)->key1));

        System.out.println("map2, (id+name)作为key: "+map2);