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 learn;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FilenameFilter;
import java.io.IOException;

public class jad2 {
public static void main(String[] args) throws IOException {
File srcDir = new File("d:\\java");
File desDir = new File("d:\\jad");
File files[] = srcDir.listFiles(new FilenameFilter() {
public boolean accept(File dir, String name) {
return  name.endsWith(".java");
}
});

if(!desDir.exists()){
desDir.mkdir();
}
for(File f : files){
FileInputStream fis = new FileInputStream(f);
String destFileName = f.getName().replaceAll("\\.java$", ".jad");
FileOutputStream fos = new FileOutputStream(new File(desDir,destFileName));
int len = 0;
byte[] buf = new byte[1024];
while((len=fis.read(buf))!=-1){
fos.write(buf,0,len);
}
fis.close();
fos.close();
}
}
}