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();
		}
	}
}