Java程序Inetaddress

Question

The question I have been asked is too write java program that reads IP address from input file and writes the corresponding host names in the output file and vice versa. here is my code:

import java.net.*;
import java.io.*;
public class hw
{
    public static void main(String args[])
    {
        try{

        FileReader f= new FileReader("w.txt");

        BufferedReader  r = new BufferedReader(f);

        FileWriter  o = new FileWriter("out.txt");
        PrintWriter p = new PrintWriter(o);


        String line = r.readLine();
        String hn=line;
        String IP;
        InetAddress d=InetAddress.getByName(hn);
        while(line !=null)
        {
        hn=d.getByName(line);
                p.println(hn);
                IP=d.getHostName();
                 p.println(IP);



    }
        r.close();
        p.close();
          }
       catch(FileNotFoundException e )
        {System.out.println("file not found");}
        catch(IOException e)
        {System.out.println("io error "+e.getMessage());}
    }//main
}//class

Answer 1

I guess your while loop never terminates. Usually I read in a loop like this:

while ((line = r.readLine()) != null) {
    // process line, i.e.
    InetAddress ia = InetAddress.getByName(line.trim());
    // etc.
}

Also you might consider putting your close statements into the finally block for good form.

Answer 2

凯文纠正你的循环错误，因为你的第二个问题，我建议你阅读本教程的读取和写入文件使用IO流