java ArrayList数据对象按排序值大小倒叙排序

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import java.util.ArrayList;import java.util.Collections;import java.util.Comparator;import java.util.List;import java.util.Random;/** *  * @author www.zuidaima.com * */public class ListSort {public static void main(String[] args) {List<User> users = new ArrayList<User>();int id = 0;User user = null;Random random = new Random();id = random.nextInt(100000);user = new User(id);user.setId(id);users.add(user);id = random.nextInt(100000);user = new User(id);user.setId(id);users.add(user);id = random.nextInt(100000);user = new User(id);user.setId(id);users.add(user);id = random.nextInt(100000);user = new User(id);user.setId(id);users.add(user);id = random.nextInt(100000);user = new User(id);user.setId(id);users.add(user);id = random.nextInt(100000);user = new User(id);user.setId(id);users.add(user);id = random.nextInt(100000);user = new User(id);user.setId(id);users.add(user);id = random.nextInt(100000);user = new User(id);user.setId(id);users.add(user);id = random.nextInt(100000);user = new User(id);user.setId(id);users.add(user);System.out.println("Before sort:");for (User _user : users) {System.out.print(_user + " ");}Collections.sort(users, new Comparator<User>() {@Overridepublic int compare(User user1, User user2) {Integer id1 = user1.getId();Integer id2 = user2.getId();                                  //可以按User对象的其他属性排序，只要属性支持compareTo方法return id2.compareTo(id1);}});System.out.println("\nAfter sort 从大到小倒序:");for (User _user : users) {System.out.print(_user + " ");}Collections.sort(users, new Comparator<User>() {@Overridepublic int compare(User user1, User user2) {Integer id1 = user1.getId();Integer id2 = user2.getId();                                //可以按User对象的其他属性排序，只要属性支持compareTo方法return id1.compareTo(id2);}});System.out.println("\nAfter sort 从小到大正序:");for (User _user : users) {System.out.print(_user + " ");}}}class User {private int id;public User(int id) {this.id = id;}public int getId() {return id;}public void setId(int id) {this.id = id;}@Overridepublic String toString() {return id + "";}}

程序运行输出结果：

Before sort:
49459 73363 18294 65350 36522 77535 38273 58512 34980
After sort 倒序:
77535 73363 65350 58512 49459 38273 36522 34980 18294
After sort 正序:
18294 34980 36522 38273 49459 58512 65350 73363 77535

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