public void testSort6(){

List<Student> studentList=new ArrayList<Student>();

Random random=new Random();

Integer id1=random.nextInt(100);

Integer id2;

Integer id3;

do{

id2=random.nextInt(100);

}while(id1==id2);

do{

id3=random.nextInt(100);

}while(id3==id2||id1==id3);

Student st1=new Student(id1+"","Jack");

Student st2=new Student(id2+"","Lucy");

Student st3=new Student(id3+"","Silence");

studentList.add(st1);

studentList.add(st2);

studentList.add(st3);

System.out.println("--------排序前--------");

for (Student student : studentList) {

System.out.println("學生為"+student.id+" ?"+student.name);

}

Collections.sort(studentList);

System.out.println("--------排序后--------");

for (Student student2 : studentList) {

System.out.println("學生為"+student2.id+" ?"+student2.name);

}

//運行了好幾次結果有時會出錯，哪里有問題嗎

//某次出錯結果如下

--------排序前--------

學生為24 ?Jack

學生為18 ?Lucy

學生為4 ?Silence

--------排序后--------

學生為18 ?Lucy

學生為24 ?Jack

學生為4 ?Silence