JAVA --- 学生信息类

import java.io.*;
import java.util.Scanner;
class Main
{
	static class student
	{
		String num,name;
		double grade1,grade2,grade3,sumgrade;
		int no;
		student(){grade1=grade2=grade3=sumgrade=0;
		num="-1";name="未知";}
		student(String a,String b,double c,double d,double e)
		{
			num=a;name=b;
			grade1=c;grade2=d;grade3=e;
			sumgrade=c+d+e;
		}
		void changeno(int x) {no=x;}
		String getnum() {return num;}
		double getsum() {return sumgrade;}
		void display() {
			System.out.print(num+"\t"+name+"\t"+grade1+"\t"+grade2+"\t"+grade3+"\t"+sumgrade+"\t");
			if(no==0) System.out.println("未知");
			else System.out.println(no);
		}
	}
	static student getstudent()throws IOException
	{
		BufferedReader cins=new BufferedReader(new InputStreamReader(System.in));
		Scanner cin=new Scanner(System.in);
		String snum=new String();
		int ok=-1;
		String sname=new String();
		String S=new String("-1");
		String p=new String();
		double d[]=new double[4];
		student s=new student();
		while(true)
		{
			try
			{
				snum=cins.readLine();
			    ok=Integer.parseInt(snum);
			}
			catch(NumberFormatException ee)
			{
				System.out.println("输入有误，请重新输入"); //只要数字组成的学号。
				continue;
			}
			if(snum.equals(S)) {break;}
			System.out.println("请输入学生姓名");
			sname=cin.next();
			for(int i=1;i<=3;i++)
			{
				System.out.println("请输入学生第"+i+"门学科成绩");
				while(true)
				{
					try
					{
						p=cins.readLine();
						if (cins.equals("-1"))
						  	   System.exit(0);
						  	 d[i]=Double.parseDouble(p);
					}
					catch(NumberFormatException ee)
					{
						System.out.println("输入有误，请重新输入");
						continue;
					}
					break;
				}
			}
			student ss=new student(snum,sname,d[1],d[2],d[3]);
			s=ss;
			break;
		}
		return s;
	}
	static int scanf(int x,student stu[])throws IOException
	{
		while(true)
		{
			System.out.println("请输入学生学号，输入-1结束输入");
			student s=getstudent();
			if(s.getnum().equals("-1")) break;
			stu[++x]=s;
		}
		return x;
	}
	static void sort(int n,student stu[])
	{
		student s=new student();
		for(int i=1;i<n;i++)
		{
			for(int j=1;j<n;j++)
			{
				if(stu[j].getsum()<stu[j+1].getsum())
				{
					s=stu[j];
					stu[j]=stu[j+1];
					stu[j+1]=s;
				}
				else if(stu[j].getsum()==stu[j+1].getsum())
				{
					if(stu[j].getnum().compareTo(stu[j+1].getnum())>0)
					{
						s=stu[j];
						stu[j]=stu[j+1];
						stu[j+1]=s;
					}
				}
			}
		}
		int num=1;
		if(n>0) stu[1].changeno(1);
		for(int i=2;i<=n;i++)
		{
			if(stu[i].getsum()==stu[i-1].getsum())
			{
				stu[i].changeno(num);
			}
			else stu[i].changeno(++num);
		}
	}
	static void display(int n,student stu[])
	{
		System.out.println("学号 \t\t 姓名 \t 成绩1 \t 成绩2 \t 成绩3 \t 总成绩  \t 名次");
		for(int i=1;i<=n;i++)
		{
			stu[i].display();
		}
	}
	static void change(int n,student stu[])throws IOException
	{
		BufferedReader cins=new BufferedReader(new InputStreamReader(System.in));
		Scanner cin=new Scanner(System.in);
		String S=new String();
		int ch=-1;
		FOR:
		while(true)
		{
			System.out.println("请输入您要修改的学生的原学号,停止修改输入-1");
			try
			{
				S=cins.readLine();
				if(S.equals("-1")) break FOR;
				ch=Integer.parseInt(S);
			}
			catch(NumberFormatException ee)
			{
				System.out.println("输入有误，请重新输入");
				continue;
			}
			for(int i=1;i<=n;i++)
			{
				if(stu[i].getnum().equals(S))
				{
					stu[i].display();
					System.out.println("请输入学生的新学号");
					stu[i]=getstudent();
				}
			}
		}
	}
	public static void main(String arg[])throws IOException
	{
		BufferedReader cins=new BufferedReader(new InputStreamReader(System.in));
		student stu[]=new student[20];
		int n=0;
		int ok=1,x;
		System.out.println("欢迎使用!");
		Scanner cin=new Scanner(System.in);
		int ch=-1;
		FOR:
		while(true)
		{
			System.out.println("请输入您的选择前的序号：");
			System.out.println("  0:      退出");
			System.out.println("  1:      输入学生信息");
			System.out.println("  2:      根据学生成绩排序");
			System.out.println("  3:      输出学生信息");
			System.out.println("  4:      修改学生信息");
			try
			{
				String s=cins.readLine();
				if(s.equals("0"))
					System.exit(0);
				ch=Integer.parseInt(s);
			}
			catch(NumberFormatException ee)
			{
				System.out.println("输入有误，请重新输入");
				continue;
			}
				switch(ch)
				{
					case 1:{n=scanf(n,stu);break;}
					case 2:{sort(n,stu);
					System.out.println("排序完成");
					break;}
					case 3:{display(n,stu);break;}
					case 4:{change(n,stu);break;}
					default: {System.out.println("输入有误，请重新输入");break;}
				}
		}
	}
}