Java：针对list中存储对象的某一属性进行排序

刺骨的言语ヽ痛彻心扉 2022-05-10 09:54 676阅读 0赞

### 前言： ###

针对list中存储的bean类，往往需要针对特定属性进行排序

### 直接贴代码是好习惯 ###

1.首先写一个简单的测试bean类

public class SortBean {
        private String name;
        private int age;
        private int userId;
    
        public SortBean(String name, int age, int userId) {
            this.name = name;
            this.age = age;
            this.userId = userId;
        }
    
        public String getName() { return name; }
        public void setName(String name) {this.name = name; }
        public int getAge() { return age; }
        public void setAge(int age) { this.age = age; }
        public int getUserId() { return userId; }
        public void setUserId(int userId) { this.userId = userId; }
    }

2.写一个main类函数直接看效果

import java.util.ArrayList;
    import java.util.Collections;
    import java.util.Comparator;
    import java.util.List;
    
    public class SortList {
        public static void main(String[] args) {
            List<SortBean> list = new ArrayList<>();
    
            SortBean sortBean0 = new SortBean("德玛", 20, 20180001);
            SortBean sortBean1 = new SortBean("寒冰", 18, 20180009);
            SortBean sortBean2 = new SortBean("流浪", 99, 20180002);
    
            list.add(sortBean0);
            list.add(sortBean1);
            list.add(sortBean2);
    
            System.out.println("before sort ");
            for (SortBean sortBean : list) {
                System.out.println("name: " + sortBean.getName() + "  age: " + sortBean.getAge());
            }
    
            Collections.sort(list, new Comparator<SortBean>() {
                @Override
                public int compare(SortBean o1, SortBean o2) {
                    if (o1.getAge() - o2.getAge() > 0) { //变成 < 可以变成递减排序
                        return 0;
                    } else {
                        return -1;
                    }
                }
            });
    
            System.out.println("after sort ");
            for (SortBean sortBean : list) {
                System.out.println("name: " + sortBean.getName() + "  age: " + sortBean.getAge());
            }
        }
    }

3.输出效果

before sort 
    name: 德玛  age: 20
    name: 寒冰  age: 18
    name: 流浪  age: 99
    after sort 
    name: 寒冰  age: 18
    name: 德玛  age: 20
    name: 流浪  age: 99

4.结语  
其实建议在把内部匿名类变成 lambda 表达式（java 8 开始支持），代码会更加简洁  
即：  
把下面代码片

Collections.sort(list, new Comparator<SortBean>() {
                @Override
                public int compare(SortBean o1, SortBean o2) {
                    if (o1.getAge() - o2.getAge() > 0) {
                        return 0;
                    } else {
                        return -1;
                    }
                }
            });

替换成

list.sort((o1, o2) -> o1.getAge() - o2.getAge()); //递减排序的话改变减号的两个对象位置

这样的话程序就更加简洁