面试题：编写程序，完成文件复制功能，即将souce.txt文件内容复制到target.txt文件中去。
代码：
package com.test;import java.io.*;public class Copyfile {/** * @param args */public static void main(String[] args) {String oldPath = "d:\\source.txt";String newPath = "d:\\target.txt";try {int bytesum = 0;int byteread = 0;File oldfile = new File(oldPath);if (oldfile.exists()) { // 文件存在时InputStream inStream = new FileInputStream(oldPath); // 读入原文件FileOutputStream fs = new FileOutputStream(newPath); byte[] buffer = new byte[1444];int length;while ((byteread = inStream.read(buffer)) != -1) {bytesum += byteread; // 字节数 文件大小System.out.println("文件字节数:" + bytesum);fs.write(buffer, 0, byteread);}inStream.close();System.out.println("文件复制成功！");} else {System.out.println(oldPath + "原文件不存在，请按这个目录" + oldPath + "来创建！");}} catch (Exception e) {System.out.println("复制单个文件操作出错");e.printStackTrace();}}}