Java: 复制文件最快、高效率的方法

Android中的文件复制--视频和图片复制

public class FileOpreateUtils {
	
	/**
	 * 
	 * @param fromFile 被复制的文件
	 * @param toFile 复制的目录文件
	 * @param rewrite 是否重新创建文件
	 * 
	 * <p>文件的复制操作方法
	 */
	public static void copyfile(File fromFile, File toFile,Boolean rewrite ){
		
		if(!fromFile.exists()){
			return;
		}
		
		if(!fromFile.isFile()){
			return;
		}
		if(!fromFile.canRead()){
			return;
		}
		if(!toFile.getParentFile().exists()){
			toFile.getParentFile().mkdirs();
		}
		if(toFile.exists() && rewrite){
			toFile.delete();
		}
		
		
		try {
			FileInputStream fosfrom = new FileInputStream(fromFile);
			FileOutputStream fosto = new FileOutputStream(toFile);
			
			byte[] bt = new byte[1024];
			int c;
			while((c=fosfrom.read(bt)) > 0){
				fosto.write(bt,0,c);
			}
			//关闭输入、输出流
			fosfrom.close();
			fosto.close();
			
			
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
	}

}

不考虑多线程优化，单线程文件复制最快的方法是(文件越大该方法越有优势，一般比常用方法快30+%):



[java] view
plaincopy

private static void nioTransferCopy(File source, File target) {

FileChannel in = null;

FileChannel out = null;

FileInputStream inStream = null;

FileOutputStream outStream = null;

try {

inStream = new FileInputStream(source);

outStream = new FileOutputStream(target);

in = inStream.getChannel();

out = outStream.getChannel();

in.transferTo(0, in.size(), out);

} catch (IOException e) {

e.printStackTrace();

} finally {

close(inStream);

close(in);

close(outStream);

close(out);

}

}



如果需要监测复制进度，可以用第二快的方法(留意buffer的大小，对速度有很大影响):

[c-sharp] view
plaincopy

private static void nioBufferCopy(File source, File target) {

FileChannel in = null;

FileChannel out = null;

FileInputStream inStream = null;

FileOutputStream outStream = null;

try {

inStream = new FileInputStream(source);

outStream = new FileOutputStream(target);

in = inStream.getChannel();

out = outStream.getChannel();

ByteBuffer buffer = ByteBuffer.allocate(4096);

while (in.read(buffer) != -1) {

buffer.flip();

out.write(buffer);

buffer.clear();

}

} catch (IOException e) {

e.printStackTrace();

} finally {

close(inStream);

close(in);

close(outStream);

close(out);

}

}



常用的方法1是:

[c-sharp] view
plaincopy

private static void customBufferBufferedStreamCopy(File source, File target) {

InputStream fis = null;

OutputStream fos = null;

try {

fis = new BufferedInputStream(new FileInputStream(source));

fos = new BufferedOutputStream(new FileOutputStream(target));

byte[] buf = new byte[4096];

int i;

while ((i = fis.read(buf)) != -1) {

fos.write(buf, 0, i);

}

}

catch (Exception e) {

e.printStackTrace();

} finally {

close(fis);

close(fos);

}

}



常用的方法2是:

[c-sharp] view
plaincopy

private static void customBufferStreamCopy(File source, File target) {

InputStream fis = null;

OutputStream fos = null;

try {

fis = new FileInputStream(source);

fos = new FileOutputStream(target);

byte[] buf = new byte[4096];

int i;

while ((i = fis.read(buf)) != -1) {

fos.write(buf, 0, i);

}

}

catch (Exception e) {

e.printStackTrace();

} finally {

close(fis);

close(fos);

}

}

延伸：

在Java编程中，复制文件的方法有很多，而且经常要用到。我以前一直是缓冲输入输出流来实现的（绝大多数人都是如此），近来在研究JDK文档时发现，用文件通道（FileChannel）来实现文件复制竟然比用老方法快了近三分之一。下面我就来介绍一下如何用文件通道来实现文件复制，以及在效率上的对比

用文件通道的方式来进行文件复制

/**

* 使用文件通道的方式复制文件

*

* @param s

* 源文件

* @param t

* 复制到的新文件

*/

public void fileChannelCopy(File s, File t) {

FileInputStream fi = null;

FileOutputStream fo = null;

FileChannel in = null;

FileChannel out = null;

try {

fi = new FileInputStream(s);

fo = new FileOutputStream(t);

in = fi.getChannel();//得到对应的文件通道

out = fo.getChannel();//得到对应的文件通道

in.transferTo(0, in.size(), out);//连接两个通道，并且从in通道读取，然后写入out通道

} catch (IOException e) {

e.printStackTrace();

} finally {

try {

fi.close();

in.close();

fo.close();

out.close();

} catch (IOException e) {

e.printStackTrace();

}

}

}

与普通的缓冲输入输出流的复制效率的对比

普通的缓冲输入输出流代码:



测试代码:



输出结果:





由此可见，FileChannel复制文件的速度比BufferedInputStream/BufferedOutputStream复制文件的速度快了近三分之一。在复制大文件的时候更加体现出FileChannel的速度优势。而且FileChannel是多并发线程安全的。