java中Comparable接口排序怎么实现自定义

class Student implements Comparable{  String name;  int gpa;  @Override  public int compareTo(Object arg0) {    // TODO Auto-generated method stub    Student s = (Student)arg0;        if(gpa == s.gpa) return name.compareTo(s.name);    else if(gpa < s.gpa) return -1;    else if(gpa > s.gpa) return 1;    else return 0;      }    }class Test {  public static void main(String[] args){    Scanner in = new Scanner(System.in);        int n = in.nextInt();        Student[] s = new Student[n];        for(int i = 0;i < n;i ++){      s[i] = new Student();      s[i].name = in.next();      s[i].gpa = in.nextInt();    }        Arrays.sort(s);        for (Student ss : s)     {       System.out.println(ss.name);       System.out.println(ss.gpa);     }   }}