在IDEA上写的可以的

源代码粘贴到上面

报这个错误

我的代码

StudentTest.java

package com.lding.sort;

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

public class StudentTest implements Comparator<Student> {

    @Override
    public int compare(Student o1, Student o2) {
        String name1=o1.getName();
        String name2=o2.getName();
        int n=name1.compareTo(name2);
        return n;
    }

    public static void main(String[] args) {
        Student one=new Student("40","peter",20);
        Student two=new Student("28","angel",5);
        Student three=new Student("35","tom",18);
        List<Student> stuList=new ArrayList<Student>();
        stuList.add(one);
        stuList.add(two);
        stuList.add(three);
        System.out.println("按名字排序前:");
        for(Student stu:stuList){
            System.out.println(stu);
        }
        Collections.sort(stuList,new StudentTest());
        System.out.println("按名字排序后:");
        for(Student stu:stuList){
            System.out.println(stu);
        }
    }
}

Student.java

​package com.lding.sort;

public class Student {
    private String id;
    private String name;
    private int age;
    public Student(){

    }

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

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    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;
    }

    @Override
    public String toString() {
        return "[" +
                "学号:" + id  +
                ",年龄:" + age  +
                ",姓名:" + name+
                ']';
    }
}

求老师帮助 哭了