Java 用Comparator对ArrayList中的对象按照该对象某属性排序

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

/**
 * Created by LSK.Reno on 2018/7/1.
 */


public class ComparableTest {
    public static void main(String[] args) {
        Comparator<Student> comparator = new Comparator<Student>(){
            public int compare(Student s1, Student s2) {
                //先排年龄
                if(s1.age!=s2.age){
                    return s2.age-s1.age;
                }
                else{
                    //年龄相同则按姓名排序
                    if(!s1.name.equals(s2.name)){
                        return s2.name.compareTo(s1.name);
                    }
                    else{
                        //姓名也相同则按学号排序
                        return s2.id-s1.id;
                    }
                }
            }
        };
        Student stu1 = new Student (1,"zhangsan","male",28,"cs");
        Student stu2 = new Student (2,"lisi","female",19,"cs");
        Student stu3 = new Student (3,"wangwu","male",22,"cs");
        Student stu4 = new Student (4,"zhaoliu","female",17,"cs");
        Student stu5 = new Student (5,"jiaoming","male",22,"cs");

        ArrayList<Student> List = new ArrayList<Student>();
        List.add(stu1);
        List.add(stu2);
        List.add(stu3);
        List.add(stu4);
        List.add(stu5);
        //这里就会自动根据规则进行排序
        Collections.sort(List,comparator);
        display(List);
    }

    static void display(ArrayList<Student> lst){
        for(Student s:lst)
            System.out.println(s);
    }
}

class Student{
    int age;
    int id;
    String gender;
    String name;
    String cs;
    Student(int id,String name,String gender,int age,String cs){
        this.age=age;
        this.name=name;
        this.gender=gender;
        this.id=id;
        this.cs=cs;
    }
    public String toString(){
        return id+"  "+name+"  "+gender+"  "+age+"  "+cs;
    }
}