刚刚学习完java.io的部分东西，写一个文件复制的小练习，包括了异常的处理（没有考虑新复制出来的文件存在的情况，直接会被覆盖掉）。 code


package io;

/*
 * 一个文本文件复制的demo
 * 1.单字节复制
 * 2. 数组复制
 */

import java.io.*;

public class FileCopyTest {
	public static void main(String[] args) {
		long s = System.currentTimeMillis();
		FileCopyByByte("test.txt","test1.txt");
		
		long m = System.currentTimeMillis();
		FileCopyByBytes("test.txt","test2.txt");
		long e = System.currentTimeMillis();
		
		
		System.out.println("单字节复制用时：" + (m-s));
		System.out.println("数组复制用时：" + (e-m));
	}
	
	/*
	 * 1.单字节复制 FileCopyByByte
	 *  结果：7757ms
	 */
	public static void FileCopyByByte(String fileAddress,String NewFileAddress){
		
		FileReader fr = null;
		FileWriter fw = null;
		
		try{
			
			fr = new FileReader(fileAddress);
			fw = new FileWriter(NewFileAddress);
			
			int len = 0;
			while((len = fr.read()) != -1){
				fw.write(len);
				fw.flush();
			}
			
		}catch(IOException e){
			throw new RuntimeException("文件复制失败");
			
		}finally{
			try{
				if(fw != null)
					fw.close();
			}catch(IOException e){
				throw new RuntimeException("关闭复制文件资源失败");
			}
			try{
				if(fr != null)
					fr.close();
			}catch(IOException e){
				throw new RuntimeException("关闭复制源资源失败");
			}

		}

	}
	
	/*
	 * 1.数组复制 FileCopyByBytes
	 * 结果：282ms
	 */
	public static void FileCopyByBytes(String fileAddress,String NewFileAddress){
		
		//创建读取写入的对象
		FileReader fr = null;
		FileWriter fw = null;
		
		try{
			//初始化读取写入的对象
			fr = new FileReader(fileAddress);
			fw = new FileWriter(NewFileAddress);
			//len存取每次读取的字符数，ch存储每次读取的内容
			int len = 0;
			char[] ch = new char[1024];
			
			//while循环写入并flush
			while((len = fr.read(ch)) != -1){
				fw.write(ch,0,len);
				fw.flush();
			}
			
			
		}catch(IOException e){
			throw new RuntimeException("文件复制失败");
			
		}finally{  //在finally里面关闭所有资源，关闭失败直接扔一个runtime异常，让程序停止
			try{
				if(fw != null)
					fw.close();
			}catch(IOException e){
				throw new RuntimeException("关闭复制文件资源失败");
			}
			try{
				if(fr != null)
					fr.close();
			}catch(IOException e){
				throw new RuntimeException("关闭复制源资源失败");
			}

		}

	}
}