jdk8 新特性之 List 排序

时间：2025-02-13 19:48:36

一、排序示例

  • 升序–> 从小到大
  • 降序–> 从大到小
  • age --> 排序字段
  • jdk8 -> Lambda 循环打印println -> (::println);
1、jdk8 -> 之前的排序(升序)
        (list, new Comparator<User>() {
            @Override
            public int compare(User o1, User o2) {
                return ().compareTo(());
            }
        });
2、jdk8 -> Lambda排序（升序）
//  不带参  
((u1, u2) -> ().compareTo(()));        
//  带参
((User u1, User u2) -> ().compareTo(()));
3、jdk8 -> Comparator 提供的静态方法排序（ 升序）
 (list, (User::getAge));
4、jdk8 -> Comparator 提供的静态方法排序（ 降序）.reversed()
(list, (User::getAge).reversed());
5、jdk8 -> 组合排序

支持每个排序字段的结尾添加.reversed() 改为降序

// Age-升序   Name-升序
(list, (User::getAge).thenComparing(User::getName));

// Age-升序   Name-降序
(list, (User::getAge).thenComparing(User::getName).reversed());

// Age-降序   Name-升序
(list, (User::getAge).reversed() .thenComparing(User::getName));

// Age-降序   Name-降序
(list, (User::getAge).reversed() .thenComparing(User::getName).reversed());

二、完整测试代码参考

package ;

import ;
import ;

import ;
import ;
import ;
import ;
import ;

public class JDK8ListSort {

    public static void main(String[] args) {


        // TODO jdk8 之前的排序
        ("============jdk8 之前的排序");
        List<User> list = initList();
        (list, new Comparator<User>() {
            @Override
            public int compare(User o1, User o2) {
                return ().compareTo(());
            }
        });
        (::println);


        // TODO jdk8 lambda 排序-升序
        ("============jdk8 lambda排序，升序排序 --> 从小到大");
        list = initList();
        ((u1, u2) -> ().compareTo(()));   //不带参  带参: ((User u1, User u2) -> ().compareTo(()));
        (::println);


        // TODO jdk8 升序排序
        ("============jdk8 升序排序 --> 从小到大，Comparator提供的静态方法");
        list = initList();
        (list, (User::getAge));
        (::println);


        // TODO jdk8 降序排序
        ("============jdk8 降序排序 --> 从大到小，Comparator提供的静态方法");
        list = initList();
        (list, (User::getAge).reversed());
        (::println);
        ();


        // TODO jdk8 组合排序
        ("============jdk8 组合排序，Comparator提供的静态方法，先按年纪排序，年纪相同的按名称排序");
        list = initList();
        (list, (User::getAge).thenComparing(User::getName));
        (::println);

    }


    /**
     * TODO  初始化List数据
     *
     * @return <.>
     * @author ws
     * @mail 1720696548@
     * @date 2020/5/10 0010 22:49
     */
    private static List<User> initList() {
        List<User> list = new ArrayList<>();
        (new User("lisa", 23));
        (new User("tom", 11));
        (new User("john", 16));
        (new User("jennis", 26));
        (new User("tin", 26));
        (new User("army", 26));
        (new User("mack", 19));
        (new User("jobs", 65));
        return list;
    }


    /**
     * TODO  测试对象
     *
     * @author ws
     * @mail 1720696548@
     * @date 2020/5/10 0010 22:49
     */
    @Data
    @AllArgsConstructor
    public static class User implements Serializable {
        private String name;
        private Integer age;
    }
}

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