java程序实现文件的备份

编写一个程序，将d:\java目录下的所有.java文件复制到d:\jad目录下，并 将原来文件的扩展名从.java改为.jad

package com.wp;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FilenameFilter;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
public class Java2Jad {

    public static void main(String[] args) throws Exception {
                     File srcDir =new File("d:\\java");

                    if(!(srcDir.exists()&& srcDir.isDirectory()))
                        throw new Exception("The directory is not exist!!");
                    File[] files= srcDir.listFiles(
                            new FilenameFilter(){
                                public boolean accept(File dir, String name) {
                                    return name.endsWith(".java");
                                }
                            }
                    );

                    System.out.println(files.length);

                    File destDir= new File("d:\\jad");
                    if(!destDir.exists())
                        destDir.mkdir();

                    for(File f:files){
                        FileInputStream fis = new FileInputStream(f);
                        String destFileName = f.getName().replaceAll("\\.java$", ".jad");
                        FileOutputStream fos = new FileOutputStream(new
                                File(destDir,destFileName));
                        copy(fis,fos);
                        fis.close();
                        fos.close();
                    }
    }

    private static void copy(InputStream ips,OutputStream ops) throws Exception{
                    int len = 0;
                    byte[] buf =new byte[1024];
                    while((len =ips.read(buf)) != -1){
                        ops.write(buf,0,len);
                    }
    }
}