【6-8完善练习】生成3个不重复的1000以内的随机正整数作为学生Id

package com.imooc.collection;

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

public class CollectionsTest {
public List<String> randomList(){
    List<String> strList=new ArrayList<String>();;
    String str;
    Random random=new Random();
    for(int i=0;i<3;i++){

        do{str=random.nextInt(999)+1+"";
        }while(strList.contains(str));
        strList.add(str);
    }
    return strList;
}

public void testSort3(){
    List<Student> studentList=new ArrayList<Student>();
    List<String> strList=randomList();
    studentList.add(new Student(strList.get(0),"Mike"));
    studentList.add(new Student(strList.get(1),"Angela"));
    studentList.add(new Student(strList.get(2),"Lucy"));
    System.out.println("------------排序前------------");
    for (Student student:studentList) {
        System.out.println("学生："+student.getStudent_id()+":"+student.getStudent_name());
    }
    Collections.sort(studentList);
    System.out.println("------------排序后------------");
    for (Student student:studentList) {
        System.out.println("学生："+student.getStudent_id()+":"+student.getStudent_name());
    }
    System.out.println("------------按照姓名排序前------------");
    for (Student student:studentList) {
        System.out.println("学生："+student.getStudent_id()+":"+student.getStudent_name());
    }
    Collections.sort(studentList,new StudentComparator());
    System.out.println("------------按照姓名排序后------------");
    for (Student student:studentList) {
        System.out.println("学生："+student.getStudent_id()+":"+student.getStudent_name());
    }
}
public static void main(String[] args) {
    CollectionsTest collectionsTest=new CollectionsTest();
     collectionsTest.testSort3();



    }
}

/*
Student类
*/
package com.imooc.collection;

import java.util.HashSet;
import java.util.Objects;
import java.util.Set;

public class Student implements Comparable<Student> {
    private String student_id;
    private String student_name;
    public Set<Course> student_course;

    public String getStudent_id(){
        return this.student_id;
    }
    public void setStudent_id(String student_id){
        this.student_id=student_id;
    }

    public String getStudent_name() {
        return this.student_name;
    }
    public void setStudent_name(String student_name) {
        this.student_name = student_name;
    }

    public Student(){

    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Student student = (Student) o;
        return Objects.equals(student_name, student.student_name);
    }

    @Override
    public int hashCode() {
        return Objects.hash(student_name);
    }



    public Student(String id, String name){
        this.student_id=id;
        this.student_name=name;
        this.student_course=new HashSet<Course>();
    }

    @Override
    public int compareTo(Student o) {
        return this.student_id.compareTo(o.student_id);
    }
}