List集合根据存储对象的属性字段排序实现

Posted 2022-12-06 Lance_xu_

1. List集合根据存储对象的属性字段排序实现

package com.huixin;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
/**
 * ListSort类
 *
 * @author Lance
 * @date 2017/03/10
 */
public class ListSort 
    public static void main(String[] args) 
        List<Student> students = new ArrayList<Student>();
        students.add(new Student("张三", 24));
        students.add(new Student("李四", 23));
        students.add(new Student("王五", 25));
        System.out.println("before sort:");
        for (Student bean : students) 
            System.out.println("before sort---->age: " + bean.getAge());
        
        Collections.sort(students);
        System.out.println("after sort:");
        for (Student bean : students) 
            System.out.println("after sort---->age: " + bean.getAge());
        
    

class Student implements Comparable<Student> 
    private String name;
    private Integer age;
    public Student(String name, Integer age) 
        this.name = name;
        this.age = age;
    

    /*
     * s的age小于this的对应字段，则返回负数；
     * 大于则返回正数；
     * 建议去了解compareTo背后的真相
     */
    @Override
    public int compareTo(Student s) 
        return s.getAge().compareTo(this.getAge());
    

    public Integer getAge() 
        return age;
    

    public void setAge(Integer age) 
        this.age = age;
    

    public String getName() 
        return name;
    

    public void setName(String name) 
        this.name = name;
    

1. 预期结果

Connected to the target VM, address: '127.0.0.1:3850', transport: 'socket'
before sort:
before sort---->age: 24
before sort---->age: 23
before sort---->age: 25
after sort:
after sort---->age: 25
after sort---->age: 24
after sort---->age: 23

======================================================
以上是java8之前的用法，java8提供了多种操作方式。博文修改2017.4.7

• 实体类

@AllArgsConstructor
@NoArgsConstructor
@Data
class Teacher 
    private String name;
    private Integer age;

• 使用Lambda表达式

 List<Teacher> teachers = new ArrayList<Teacher>();
        teachers.add(new Teacher("张三", 24));
        teachers.add(new Teacher("李四", 23));
        teachers.add(new Teacher("王五", 25));
        System.out.println("before sort:");
        for (Teacher bean : teachers) 
            System.out.println("before sort---->age: " + bean.getAge());
        
        //Lambda
        teachers.sort((s1, s2) -> s1.getAge().compareTo(s2.getAge()));
        System.out.println("after sort:");
        for (Teacher bean : teachers) 
            System.out.println("after sort---->age: " + bean.getAge());
        

• 使用Comparator操作器

//Comparator
        Collections.sort(teachers, Comparator.comparing(Teacher::getAge));

• 反序排列

Comparator<Teacher> comparator = (t1, t2) -> t1.getAge().compareTo(t2.getAge());
        teachers.sort(comparator.reversed());

• 组合排序

//组合排序
        teachers.sort(Comparator.comparing(Teacher::getAge).thenComparing(Teacher::getName));

• 完整示例代码

package com.huixin.utils.common;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

/**
 * ListSort类
 *
 * @author Lance
 * @date 2017/03/10
 */
public class ListSortJava8 
    public static void main(String[] args) 
        List<Teacher> teachers = new ArrayList<Teacher>();
        teachers.add(new Teacher("张三", 24));
        teachers.add(new Teacher("李四", 23));
        teachers.add(new Teacher("王五", 25));
        teachers.add(new Teacher("钱二", 23));
        System.out.println("before sort:");
        for (Teacher bean : teachers) 
            System.out.println("before sort---->age: " + bean.getAge() + "==name：" + bean.getName());
        
        //Lambda
//        teachers.sort((t1, t2) -> s1.getAge().compareTo(s2.getAge()));
        //Comparator
//        Collections.sort(teachers, Comparator.comparing(Teacher::getAge));
        //reversed
//        Comparator<Teacher> comparator = (t1, t2) -> t1.getAge().compareTo(t2.getAge());
//        teachers.sort(comparator.reversed());
        //组合排序
        teachers.sort(Comparator.comparing(Teacher::getAge).thenComparing(Teacher::getName));
        System.out.println("after sort:");
        for (Teacher bean : teachers) 
            System.out.println("after sort---->age: " + bean.getAge() + "==name：" + bean.getName());
        
    


@AllArgsConstructor
@NoArgsConstructor
@Data
class Teacher 
    private String name;
    private Integer age;