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
	 * 
	 * 
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+%):

 

 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):

 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:

 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:

 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

1. 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();

               }

           }

       }

2. 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:

   

3. 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。