Dada_WenJian

 import java.io.BufferedReader;
 import java.io.File;
 import java.io.FileReader;
 import java.io.FileWriter;
 import java.io.PrintWriter;
 import java.util.Scanner;

 public class F1_F2_copy {

     public void F1_F2(File f1,File f2)
     {
         try
         {

             int i=1;
             //写入f2
             FileWriter fw=new FileWriter(f2,false);
             PrintWriter pw=new PrintWriter(fw);
             //阅读f1
             Scanner shuru = new Scanner(new BufferedReader(new FileReader(f1)));
         while(shuru.hasNext())
         {
             pw.println(i+"  "+shuru.next());//插入行号
             i++;
         }

             pw.flush();
             pw.close();
             fw.close();

         }
         catch(Exception e)
         {
             System.out.println("错误");
         }

     }
 }

对一个空文本复制一个有行号的文本