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();

		}

	}

}