比较器的使用

package com.ljs.day1;

import java.util.Arrays;
import java.util.Comparator;

public class CompareDemo {
    
    public static void main(String[] args) {
        Student st1 = new Student(4, "ljs", 100);
        Student st2 = new Student(8, "it", 90);
        Student st3 = new Student(2, "que", 80);
        Student [] studens = new Student[] {st1,st2,st3}; 
        
        Arrays.sort(studens,new CompareByGrade());
        System.out.println(studens[0].toString());
        System.out.println(studens[1].toString());
        System.out.println(studens[2].toString());
        
    }

}

class Student{
    int id;
    String name;
    int grade;
    
    public Student(int id, String name, int grade){
        this.id = id;
        this.name = name;
        this.grade = grade;
    }

    public String toString() {
        return "Student [id=" + id + ", name=" + name + ", grade=" + grade + "]";
    }
    
}
class CompareById implements Comparator<Student>{

    public int compare(Student o1, Student o2) {
        return o1.id - o2.id;
    }
}

class CompareByGrade implements Comparator<Student>{

    @Override
    public int compare(Student o1, Student o2) {
        return o1.grade - o2.grade;
    }
    
}