学生信息小程序(实现追加,读取的方法,java语言编写)

import java.io.*;
import java.util.*;
public class du
{
private final static int num[] = new int[2],age[]=new int[2];
private final static String name[]=new String[2];
public static void main(String[] args) throws Exception {
Scanner scanner=new Scanner(System.in);
//建立一个RandomAccessFile 文件对象用于追加
RandomAccessFile in=new RandomAccessFile("D:\\do.txt","rw");
InputStreamReader ir=new InputStreamReader(System.in);
BufferedReader du;
for(int i=0;i<num.length;i++)
{
//先计算出文件filename的长度
long filename=in.length();
//每次读取将指针放到上一次的文本的末尾便于追加
in.seek(filename);
System.out.print("please input number : ");
du=new BufferedReader(ir);
//利用数组保存数据为方便后面查询功能
num[i] =Integer.parseInt(du.readLine());
in.writeBytes("the num is :"+num[i]+" ");
System.out.print("please input name : ");
du=new BufferedReader(ir);
String h=du.readLine();
in.writeBytes("the name is :"+h+" ");
name[i]=h;
System.out.print("please input age:");
du=new BufferedReader(ir);
age[i]=Integer.parseInt(du.readLine());
in.writeBytes("the age is :"+age[i]+" "+"\n");
}
in.close();
//为了方便后面写的较简单
System.out.println("请做出选择：");
System.out.println("1--->显示数据");
System.out.println("2--->查询数据");
System.out.println("3--->显示平均年龄");
int b=0;
b=scanner.nextInt();
switch(b)
{
case(1):
System.out.println("输出文件中的数据：");
BufferedReader bu=new BufferedReader(new FileReader("D:\\do.txt"));
String line=bu.readLine();
//一行一行的读取
while(line!=null)
{ System.out.println(line+"\n");
line=bu.readLine();
}
bu.close();
case(2):
System.out.println("请输入要查询的学号:");
int c=0;
c=scanner.nextInt();
for(int i=0;i<num.length;i++)
{
if(c==num[i])
{
System.out.println("the num is :"+num[i]+"\n");
System.out.println("the name is :"+name[i]+"\n");
System.out.println("the age is :"+age[i]+"\n");
}
}
case(3):
int sum=0;
for(int i=0;i<age.length;i++)
{
sum=sum+age[i];
}
System.out.println("平均年龄为: "+sum/age.length);
break;
}
}
}。