Java实现文件拷贝

   经过一组简单的测试发现JAVA NIO提供的文件内存映射方法实现文件拷贝速度最快，不管是大文件还是小文件，特别是大文件的拷贝速度比普通方法提高20倍，唯一有个前提就是内存需要足够大，否则文件映射肯定失败（当然可以通过分割文件，部分映射的方法避免，但就比较麻烦了）；其次NIO提供的文件管道传输速度也比较好，如果没法做文件内存映射，推荐这种拷贝方法；另外，Buffer的大小，对于读写速度还是有影响的，基本就是Buffer越大读写越快（有个疑问就是Buffer.allocateDirec()效率提高不明显）；最后，总体看来NIO的效率比老IO高，不管使用哪种方式，老IO使用流读写只能一个字节一个字节的抠，NIO使用块的方式读写还是相对比较快，所以没有特别需求的情况下，推荐使用NIO，目前NIO基本能覆盖老IO的所有功能（当然NIO还提供N多新功能）。

• 测试环境

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Eclipse(Juno) JVM(Sun JDK1.7) 参数： -Xms1536m -Xmx1536m -Xverify:none -XX:+UseParallelGC -XX:PermSize=128M -XX:MaxPermSize=128M OS参数： Win7 64Bit + 4GB 物理磁盘空间充足

• 测试代码

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importjava.io.FileInputStream; importjava.io.FileNotFoundException; importjava.io.FileOutputStream; importjava.io.IOException; importjava.io.RandomAccessFile; importjava.nio.ByteBuffer; importjava.nio.MappedByteBuffer; importjava.nio.channels.FileChannel; publicclassFileCopy { privatestaticfinalintBUFFER_SIZE_1024 = 1024; privatestaticfinalintBUFFER_SIZE_4096 = 4096; privatestaticfinalintBUFFER_SIZE_10240 = 10240; privatestaticfinalString FROM_FILE_42MB = "G:/from_42MB.rar"; privatestaticfinalString FROM_FILE_1GB = "G:/from_350MB.rar"; privatestaticintBUFFER_SIZE = BUFFER_SIZE_1024; privatestaticString FROM_FILE = FROM_FILE_42MB; /** * @param args * @throws Exception */ publicstaticvoidmain(String[] args) throwsException { System.out.println("File :"+ FROM_FILE + " ---- Buffer Size : "+ BUFFER_SIZE + "--------------"); testFileCopy(); BUFFER_SIZE = BUFFER_SIZE_4096; System.out.println("File :"+ FROM_FILE + " ---- Buffer Size : "+ BUFFER_SIZE + "--------------"); testFileCopy(); BUFFER_SIZE = BUFFER_SIZE_10240; System.out.println("File :"+ FROM_FILE + " ---- Buffer Size : "+ BUFFER_SIZE + "--------------"); testFileCopy(); BUFFER_SIZE = BUFFER_SIZE_1024; FROM_FILE = FROM_FILE_1GB; System.out.println("File :"+ FROM_FILE + " ---- Buffer Size : "+ BUFFER_SIZE + "--------------"); testFileCopy(); BUFFER_SIZE = BUFFER_SIZE_4096; FROM_FILE = FROM_FILE_1GB; System.out.println("File :"+ FROM_FILE + " ---- Buffer Size : "+ BUFFER_SIZE + "--------------"); testFileCopy(); BUFFER_SIZE = BUFFER_SIZE_10240; FROM_FILE = FROM_FILE_1GB; System.out.println("File :"+ FROM_FILE + " ---- Buffer Size : "+ BUFFER_SIZE + "--------------"); testFileCopy(); } privatestaticvoidtestFileCopy() throwsFileNotFoundException, IOException { coypByMbb(); copyByNioTransferFrom(); copyByNioTransferTo(); coypByBufferRead(); coypByFastBufferRead();           coypByStream();//Old IO style } /** * 使用FileChannel.transferFrom()实现 * @throws FileNotFoundException * @throws IOException */ privatestaticvoidcopyByNioTransferFrom() throwsFileNotFoundException, IOException { longstartTime = System.currentTimeMillis(); RandomAccessFile fromFile = newRandomAccessFile(FROM_FILE, "rw"); FileChannel fromChannel = fromFile.getChannel(); RandomAccessFile toFile = newRandomAccessFile("G:/to1.rar", "rw"); FileChannel toChannel = toFile.getChannel(); longposition = 0; longcount = fromChannel.size(); toChannel.transferFrom(fromChannel, position, count); longendTime = System.currentTimeMillis(); System.out.println("copyByNioTransferFrom time consumed(buffer size no effect) : " + (endTime - startTime)); } /** * 使用FileChannel.transferTo()实现 * @throws FileNotFoundException * @throws IOException */ privatestaticvoidcopyByNioTransferTo() throwsFileNotFoundException, IOException { longstartTime = System.currentTimeMillis(); RandomAccessFile fromFile = newRandomAccessFile(FROM_FILE, "rw"); FileChannel fromChannel = fromFile.getChannel(); RandomAccessFile toFile = newRandomAccessFile("G:/to2.rar", "rw"); FileChannel toChannel = toFile.getChannel(); longposition = 0; longcount = fromChannel.size(); fromChannel.transferTo(position, count, toChannel); longendTime = System.currentTimeMillis(); System.out.println("copyByNioTransferTo time consumed(buffer size no effect) : " + (endTime - startTime)); } /** * 使用Channel, Buffer简单读写实现 * @throws IOException */ privatestaticvoidcoypByBufferRead() throwsIOException { longstartTime = System.currentTimeMillis(); FileInputStream fin = newFileInputStream(FROM_FILE); FileOutputStream fout = newFileOutputStream("G:/to3.rar"); FileChannel fcin = fin.getChannel(); FileChannel fcout = fout.getChannel(); ByteBuffer buffer = ByteBuffer.allocate(BUFFER_SIZE); while(true) { buffer.clear(); intr = fcin.read(buffer); if(r == -1) { break; } buffer.flip(); fcout.write(buffer); } longendTime = System.currentTimeMillis(); System.out.println("coypByBufferRead time consumed(buffer size take effect) : " + (endTime - startTime)); } /** * 使用连续内存的Buffer实现 * @throws IOException */ privatestaticvoidcoypByFastBufferRead() throwsIOException { longstartTime = System.currentTimeMillis(); FileInputStream fin = newFileInputStream(FROM_FILE); FileOutputStream fout = newFileOutputStream("G:/to4.rar"); FileChannel fcin = fin.getChannel(); FileChannel fcout = fout.getChannel(); ByteBuffer buffer = ByteBuffer.allocateDirect(BUFFER_SIZE); while(true) { buffer.clear(); intr = fcin.read(buffer); if(r == -1) { break; } buffer.flip(); fcout.write(buffer); } longendTime = System.currentTimeMillis(); System.out.println("coypByFastBufferRead time consumed(buffer size take effect) : " + (endTime - startTime)); } /** * 使用文件内存映射实现 * @throws IOException */ privatestaticvoidcoypByMbb() throwsIOException { longstartTime = System.currentTimeMillis(); FileInputStream fin = newFileInputStream(FROM_FILE); RandomAccessFile fout = newRandomAccessFile("G:/to5.rar", "rw"); FileChannel fcin = fin.getChannel(); FileChannel fcout = fout.getChannel(); MappedByteBuffer mbbi = fcin.map(FileChannel.MapMode.READ_ONLY, 0, fcin.size()); MappedByteBuffer mbbo = fcout.map(FileChannel.MapMode.READ_WRITE, 0, fcin.size()); mbbo.put(mbbi); mbbi.clear(); mbbo.clear(); longendTime = System.currentTimeMillis(); System.out .println("coypByMbb time consumed(buffer size no effect) : "+ (endTime - startTime)); } /** * 使用传统IO的流读写方式实现 * @throws IOException */ privatestaticvoidcoypByStream() throwsIOException { longstartTime = System.currentTimeMillis(); FileInputStream fin = newFileInputStream(FROM_FILE); FileOutputStream fout = newFileOutputStream("G:/to6.rar"); byte[] buffer = newbyte[BUFFER_SIZE]; while(true) { intins = fin.read(buffer); if(ins == -1) { fin.close(); fout.flush(); fout.close(); break; } else{ fout.write(buffer, 0, ins); }             } longendTime = System.currentTimeMillis(); System.out.println("coypByStream time consumed(buffer size take effect) : "+ (endTime - startTime)); } }

• 测试结果

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  File :G:/from_42MB.rar ---- Buffer Size : 1024-------------- coypByMbb time consumed(buffer size no effect) : 47 copyByNioTransferFrom time consumed(buffer size no effect) : 62 copyByNioTransferTo time consumed(buffer size no effect) : 47 coypByBufferRead time consumed(buffer size take effect) : 249 coypByFastBufferRead time consumed(buffer size take effect) : 188 coypByStream time consumed(buffer size take effect) : 187 File :G:/from_42MB.rar ---- Buffer Size : 4096-------------- coypByMbb time consumed(buffer size no effect) : 15 copyByNioTransferFrom time consumed(buffer size no effect) : 16 copyByNioTransferTo time consumed(buffer size no effect) : 31 coypByBufferRead time consumed(buffer size take effect) : 125 coypByFastBufferRead time consumed(buffer size take effect) : 79 coypByStream time consumed(buffer size take effect) : 93 File :G:/from_42MB.rar ---- Buffer Size : 10240-------------- coypByMbb time consumed(buffer size no effect) : 16 copyByNioTransferFrom time consumed(buffer size no effect) : 32 copyByNioTransferTo time consumed(buffer size no effect) : 31 coypByBufferRead time consumed(buffer size take effect) : 78 coypByFastBufferRead time consumed(buffer size take effect) : 62 coypByStream time consumed(buffer size take effect) : 63 File :G:/from_350MB.rar ---- Buffer Size : 1024-------------- coypByMbb time consumed(buffer size no effect) : 280 copyByNioTransferFrom time consumed(buffer size no effect) : 453 copyByNioTransferTo time consumed(buffer size no effect) : 7785 coypByBufferRead time consumed(buffer size take effect) : 8144 coypByFastBufferRead time consumed(buffer size take effect) : 7068 coypByStream time consumed(buffer size take effect) : 8503 File :G:/from_350MB.rar ---- Buffer Size : 4096-------------- coypByMbb time consumed(buffer size no effect) : 1904 copyByNioTransferFrom time consumed(buffer size no effect) : 5978 copyByNioTransferTo time consumed(buffer size no effect) : 7379 coypByBufferRead time consumed(buffer size take effect) : 7621 coypByFastBufferRead time consumed(buffer size take effect) : 7474 coypByStream time consumed(buffer size take effect) : 8200 File :G:/from_350MB.rar ---- Buffer Size : 10240-------------- coypByMbb time consumed(buffer size no effect) : 328 copyByNioTransferFrom time consumed(buffer size no effect) : 6864 copyByNioTransferTo time consumed(buffer size no effect) : 7021 coypByBufferRead time consumed(buffer size take effect) : 7199 coypByFastBufferRead time consumed(buffer size take effect) : 7941 coypByStream time consumed(buffer size take effect) : 7801