这一段代码里是怎么用实现排序的？希望可以详细讲解一下相关的知识点

abstract class Compare implements Comparator{
	//抽象方法
	abstract public int compare(Object o1, Object o2);
}

//学号比较器接口,继承抽象类
class CompareByStuId extends Compare{
	//比较学号
	public int compare(Object o1, Object o2) {
		Student s1=(Student)o1;
		Student s2=(Student)o2;
		return s1.stuId.compareTo(s2.stuId);
	}
}

public class MainTest {
	public static void main(String[] args) {
            Student[] stus;
			stus=readStudentFile();
			
			ArrayList stuList;
			String nameId; //保存学号或者姓名

				//按学号升序排序输出,抽象父类的引用，子类的对象
					Compare cbn=new CompareByStuId();
					stuList=sort(stus,cbn);
					for (int i = 0; i < stus.length; i++) {
						stus[i]=(Student)stuList.get(i);
					}
					printData(stus);//输出所有
}

	//根据传入的是Compare的哪个子类，按照学号排序的方法，
	public static ArrayList sort(Student[] stus,Compare cmp){
		ArrayList stuList=new ArrayList();
		for (int i = 0; i < stus.length; i++) {
			stuList.add(stus[i]);
		}
		Collections.sort(stuList,cmp);
		return stuList;
	}
}


public class Student {
	//属性
	String stuId;
	String stuName;
	String sex;
	String college;
	int[] scores=new int[10];
	int avg;
	
	//构造方法
	Student(){
		
	}
	Student(String stuId,String stuName,String sex,String college){
		this.stuId=stuId;
		this.stuName=stuName;
		this.sex=sex;
		this.college=college;
	}
}

使用集合排序，Collections.sort(stuList,cmp);

关键的代码是排序接口：

abstract class Compare implements Comparator{
	//抽象方法
	abstract public int compare(Object o1, Object o2);
}
 
//学号比较器接口,继承抽象类
class CompareByStuId extends Compare{
	//比较学号
	public int compare(Object o1, Object o2) {
		Student s1=(Student)o1;
		Student s2=(Student)o2;
		return s1.stuId.compareTo(s2.stuId);
	}
}