lamda -- 排序

- 日理万妓 2023-02-22 08:27 36阅读 0赞

### LamadSort.java ###

package com.example.demo.util;
    
    import com.example.demo.entity.User;
    
    import java.util.*;
    import java.util.stream.Collectors;
    
    public class LamadSort{ 
        public static void main(String[] args) { 
            System.out.println("list集合:");
            test1();
    
            System.out.println("\nmap按ASCII排序:");
            test2();
    
            System.out.println("\n对象属性:");
            test3();
    
            System.out.println("\n数组:");
            test4();
        }
    
        /** * 排序 -- list集合 */
        public static void test1() { 
            //1. 初始化数据
            List<User> users = new ArrayList<User>();
            User u1 = new User(2, "刘德华");
            User u2 = new User(3, "彭于晏");
            User u3 = new User(1, "林峰");
            users.add(u1);
            users.add(u2);
            users.add(u3);
    
            //2. 排序 -- 方式一
            //Collections.sort(users, Comparator.comparing(User::getId));
    
            // 排序 -- 方式二
            Collections.sort(users, (uer1, uer2) -> uer1.getId().compareTo(uer2.getId()));
    
            //3. 输出
            users.forEach(user -> { 
                System.out.println("id = " + user.getId() + ",name = " + user.getName());
            });
        }
    
        /** * 排序 -- map按ASCII排序 */
        public static void test2() { 
            //1. 初始化数据
            Map<String, Integer> map = new HashMap();
            map.put("key1",10);
            map.put("key2",13);
            map.put("key3",11);
            map.put("key4",14);
            map.put("key5",12);
    
            //2. 排序
            map = map.entrySet()
                    .stream()
                    .sorted(Map.Entry.<String, Integer>comparingByValue())
                    .collect(Collectors.toMap(k -> k.getKey(), v -> v.getValue(),
                            (k, v) -> k, LinkedHashMap::new));
    
            //3. 输出
            map.forEach((key, value) -> { 
                System.out.println("Key: " + key + ", Value: " + value);
            });
        }
    
        /** * 排序 -- 对象属性 */
        public static void test3() { 
            //1. 初始化数据
            List<User> users = new ArrayList<User>();
            User u1 = new User(2, "刘德华");
            User u2 = new User(3, "彭于晏");
            User u3 = new User(1, "林峰");
            users.add(u1);
            users.add(u2);
            users.add(u3);
    
            System.out.println("------------升序---------------");
            //2. 升序
            List<User> userAscList = users.stream().sorted(Comparator.comparing(User::getId))
                    .collect(Collectors.toList());
    
            //3. 输出
            userAscList.forEach(user -> { 
                System.out.println("id = " + user.getId() + ",name = " + user.getName());
            });
    
            System.out.println("------------降序---------------");
            //2. 降序
            List<User> userDescList = users.stream().sorted(Comparator.comparing(User::getId).reversed())
                    .collect(Collectors.toList());
    
            //3. 输出
            userDescList.forEach(user -> { 
                System.out.println("id = " + user.getId() + ",name = " + user.getName());
            });
        }
    
        /** * 排序 -- 数组 */
        public static void test4(){ 
            //1. 初始化数据
            String[] datas = { "2016-06-28 08:00:00",
                    "2017-12-05 19:17:32",
                    "2017-03-06 22:14:51",
                    "2016-12-28 08:00:00",
                    "2017-03-05 19:17:32",
                    "2017-03-06 22:14:51"};
    
            //2. 排序
            Arrays.sort(datas, (String s1, String s2) -> (s1.compareTo(s2)));
    
            //3. 输出
            Arrays.stream(datas).forEach(System.out::println);
        }
    }

### User.java ###

package com.example.demo.entity;
    
    public class User { 
        private Integer id;
        private String name;
    
        public User(Integer id, String name) { 
            this.id = id;
            this.name = name;
        }
    
        public Integer getId() { 
            return id;
        }
    
        public void setId(Integer id) { 
            this.id = id;
        }
    
        public String getName() { 
            return name;
        }
    
        public void setName(String name) { 
            this.name = name;
        }
    
        @Override
        public String toString() { 
            return "User{" +
                    "id=" + id +
                    ", name='" + name + '\'' +
                    '}';
        }
    }

### 输出 ###

list集合:
    id = 1,name = 林峰
    id = 2,name = 刘德华
    id = 3,name = 彭于晏
    
    map按ASCII排序:
    Key: key1, Value: 10
    Key: key3, Value: 11
    Key: key5, Value: 12
    Key: key2, Value: 13
    Key: key4, Value: 14
    
    对象属性:
    ------------升序---------------
    id = 1,name = 林峰
    id = 2,name = 刘德华
    id = 3,name = 彭于晏
    ------------降序---------------
    id = 3,name = 彭于晏
    id = 2,name = 刘德华
    id = 1,name = 林峰
    
    数组:
    2016-06-28 08:00:00
    2016-12-28 08:00:00
    2017-03-05 19:17:32
    2017-03-06 22:14:51
    2017-03-06 22:14:51
    2017-12-05 19:17:32