用java写一个学生类，对总成绩降序排列输出并打印名次

要求：编写一个学生类，输入姓名，学号，三门课成绩，然后按总分降序排列输出，并打印名次，如果总分相同，输出同样的名次，如1 2 2 3 4
刚开始学java，只能写到下面那样了，输出名次完全没有思路，排序也感觉怪怪的，有没有大佬能够指点一下QAQ

import java.util.Arrays;
public class Student {
public String name;
public int xuehao,mingci;
public double a1,a2,a3;
Student(int xuehao,String name,double a1,double a2,double a3){
this.xuehao=xuehao;
this.name=name;
this.a1=a1;
this.a2=a2;
this.a3=a3;
}
double sum(){
return(this.a1+this.a2+this.a3);
}
}
public class Test {
public static void main(String[] args){
Student student[]=new Student[5];
double s[]=new double[5];
student[0]=new Student(20160001,"学生一",85,72,95);
student[1]=new Student(20160002,"学生二",87,88,92);
student[2]=new Student(20160003,"学生三",20,60,56);
student[3]=new Student(20160004,"学生四",99,94,56);
student[4]=new Student(20160005,"学生五",100,100,100);
for(int j=0;j<5;j++){
s[j]=student[j].sum();
}
Arrays.sort(s);
for(int j=4;j>=0;j--){
for(int i=0;i<5;i++){
if(student[i].sum()==s[j])
System.out.println(student[i].xuehao+" "+student[i].name+" "+student[i].a1+" "+
student[i].a2+" "+student[i].a3+" 总分:"+student[i].sum());
}
}
}
}