Java8对List集合对象某个字段进行排序

一、准备工作

　　1、声明一个对象

class User{
        private Integer userId;
        private String userName;
 
        public Integer getUserId() {
            return userId;
        }
 
        public void setUserId(Integer userId) {
            this.userId = userId;
        }
 
        public String getUserName() {
            return userName;
        }
 
        public void setUserName(String userName) {
            this.userName = userName;
        }
 
        public User(Integer userId, String userName) {
            this.userId = userId;
            this.userName = userName;
        }
 
        public User() {
        }
 
        @Override
        public String toString() {
            return "User{" +
                    "userId=" + userId +
                    ", userName='" + userName + '\'' +
                    '}';
        }
    }

二、开始测试

　　1、测试代码

@Test
    public void lambdaTest1(){
        List<User> list = new ArrayList<>();
        list.add(new User(1,"张三"));
        list.add(new User(4,"赵六"));
        list.add(new User(2,"李四"));
        list.add(new User(3,"王五"));
            
        //条件删除
        list.removeIf(user -> user.getUserId() == 3);
        System.out.println("--------------排序前");
        list.forEach(user -> {
            System.out.println(user);
        });
        list.sort((user1,user2)->user1.getUserId() - user2.getUserId());
        System.out.println("_-------------------正序排序后");
        list.forEach(user -> {
            System.out.println(user);
        });
 
        System.out.println("--------------------倒序排序后：");
        list.sort((((o1, o2) -> o2.getUserId() - o1.getUserId())));
        list.forEach(user -> {
            System.out.println(user);
        });
    }

　　2、输出结果