帮我看下这个关于继承程序！

import java.util.Scanner;
abstract class person
{
    String name;
  String sex;
  int age;
  
  protected void person()
  {
      Scanner reader=new Scanner(System.in);
      System.out.print("请输入姓名：");
         name=reader.nextLine();

         System.out.print("请输入性别：");
         sex=reader.nextLine();
         
         System.out.print("请输入年龄：");
    age=reader.nextInt();
    }
   
    abstract public void show1();
/*    abstract public void show2();*/
}

class student extends person
{
  String num;
  String classdry;
  /*double chinese;
  double math;
  double english;*/
  static String course;
  static double score;
  static double sum=0;
  
  public static double total(int m)
    {
     int i;
     for(i=0;i<m-1;i++)
     {sum=sum+score;
      //   System.out.print("\n总分："+sum);
         }
    return(sum);
     
    }

  public static double average(int m)
   {
   
    double avg;
    avg=sum/m;
    //System.out.print("平均分："+avg);
    return(avg);
  }
  
  protected void print1()
  {
      
       Scanner reader=new Scanner(System.in);
       System.out.println("请输入学生基本信息！");

       System.out.print("请输入学号：");
     num=reader.nextLine();
      
       super.person();
      
          System.out.print("请输入是否是班干部：");
          classdry=reader.nextLine();
         
          /*System.out.print("请输入语文成绩：");
          chinese=reader.nextInt();

          System.out.print("请输入数学成绩：");
          math=reader.nextInt();

          System.out.print("请输入外语成绩：");
     english=reader.nextInt();*/
     }
   
   public static void print2(student stu[],int m)
     {
         for(int j=0;j<m;j++)
         {
             Scanner reader=new Scanner(System.in);
             System.out.println("请输入课程名及其成绩：");
             course=reader.nextLine();
             score=reader.nextDouble();
             System.out.println(course+"的成绩"+score);
         }
    }
     
     public void show1()
     {
         System.out.print("学号："+num+"  "+"姓名："+name+"  "+"性别："+sex+"  "+"年龄:"+age+"  "+"是否是班干："+classdry);
    }
   
   /* public void show2()
    {
     System.out.print("\n"+course+"成绩"+score);
    }*/
  
   
 /* public static  void  sorting(student stu[],int n)
   {
    int i,j;
    student t;
    for(j=0;j<n-1;j++)
    for(i=0;i<n-1-j;i++)
    if(stu[i].total()<stu[i+1].total())
    {t=stu[i];stu[i]=stu[i+1];stu[i+1]=t;}
    for(i=0;i<n;i++)
    System.out.println("第"+(i+1)+"名为:"+stu[i].name+"总分为："+stu[i].total());
  }*/
}


class computer extends student
{
 private String department;
// private double java;
 
 void comstudent(String dep)
 {
     department=dep;
     System.out.print("  系别："+department);
 }
}
  
  
  
class allstudent
 {
      public static void main(String args[])
      {            
           int n,m;
     Scanner reader=new Scanner(System.in);
     System.out.print("请输入你想输入多少个学生资料:");
     n=reader.nextInt();
     System.out.print("请输入你想输入的课程数：");
     m=reader.nextInt();
           computer stu[];
     stu=new computer[n];
                 
     for(int i=0;i<n;i++)
     {
      stu[i]=new computer();
      stu[i].print1();
      computer.print2(stu,m);
      stu[i].show1();
      stu[i].comstudent("计算机科学系");
      //stu[i].show2();
      System.out.print("\n总分为"+student.total(m)+","+"平均分为"+student.average(m));
      System.out.println();
      }
      
               
         // computer.sorting(stu,n);
     }
}

其中算总分和平均分那里不知道怎么写！上面的程序就那里有问题!但找不出来！能运行，但算的总分错的！