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

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

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
public class FileCopy {
private static final int BUFFER_SIZE_1024 = 1024 ;
private static final int BUFFER_SIZE_4096 = 4096 ;
private static final int BUFFER_SIZE_10240 = 10240 ;

private static final String FROM_FILE_42MB = "G:/from_42MB.rar" ;
private static final String FROM_FILE_1GB = "G:/from_350MB.rar" ;

private static int BUFFER_SIZE = BUFFER_SIZE_1024;
private static String FROM_FILE = FROM_FILE_42MB;
/**
* @param args
* @throws Exception
*/
public static void main(String[] args) throws Exception {
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();

}
private static void testFileCopy() throws FileNotFoundException,
IOException {
coypByMbb();
copyByNioTransferFrom();
copyByNioTransferTo();
coypByBufferRead();
coypByFastBufferRead();
coypByStream(); //Old IO style
}
/**
* 使用FileChannel.transferFrom()实现
* @throws FileNotFoundException
* @throws IOException
*/
private static void copyByNioTransferFrom() throws FileNotFoundException,
IOException {
long startTime = System.currentTimeMillis();
RandomAccessFile fromFile = new RandomAccessFile(FROM_FILE, "rw" );
FileChannel fromChannel = fromFile.getChannel();
RandomAccessFile toFile = new RandomAccessFile( "G:/to1.rar" , "rw" );
FileChannel toChannel = toFile.getChannel();
long position = 0 ;
long count = fromChannel.size();
toChannel.transferFrom(fromChannel, position, count);
long endTime = System.currentTimeMillis();
System.out.println( "copyByNioTransferFrom time consumed(buffer size no effect) : "
+ (endTime - startTime));
}
/**
* 使用FileChannel.transferTo()实现
* @throws FileNotFoundException
* @throws IOException
*/
private static void copyByNioTransferTo() throws FileNotFoundException,
IOException {
long startTime = System.currentTimeMillis();
RandomAccessFile fromFile = new RandomAccessFile(FROM_FILE, "rw" );
FileChannel fromChannel = fromFile.getChannel();
RandomAccessFile toFile = new RandomAccessFile( "G:/to2.rar" , "rw" );
FileChannel toChannel = toFile.getChannel();
long position = 0 ;
long count = fromChannel.size();
fromChannel.transferTo(position, count, toChannel);
long endTime = 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
*/
private static void coypByBufferRead() throws IOException {
long startTime = System.currentTimeMillis();
FileInputStream fin = new FileInputStream(FROM_FILE);
FileOutputStream fout = new FileOutputStream( "G:/to3.rar" );
FileChannel fcin = fin.getChannel();
FileChannel fcout = fout.getChannel();
ByteBuffer buffer = ByteBuffer.allocate(BUFFER_SIZE);
while ( true ) {
buffer.clear();
int r = fcin.read(buffer);
if (r == - 1 ) {
break ;
}
buffer.flip();
fcout.write(buffer);
}
long endTime = 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
*/
private static void coypByFastBufferRead() throws IOException {
long startTime = System.currentTimeMillis();
FileInputStream fin = new FileInputStream(FROM_FILE);
FileOutputStream fout = new FileOutputStream( "G:/to4.rar" );
FileChannel fcin = fin.getChannel();
FileChannel fcout = fout.getChannel();
ByteBuffer buffer = ByteBuffer.allocateDirect(BUFFER_SIZE);
while ( true ) {
buffer.clear();
int r = fcin.read(buffer);
if (r == - 1 ) {
break ;
}
buffer.flip();
fcout.write(buffer);
}
long endTime = 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
*/
private static void coypByMbb() throws IOException {
long startTime = System.currentTimeMillis();
FileInputStream fin = new FileInputStream(FROM_FILE);
RandomAccessFile fout = new RandomAccessFile( "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();
long endTime = 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
*/
private static void coypByStream() throws IOException {
long startTime = System.currentTimeMillis();
FileInputStream fin = new FileInputStream(FROM_FILE);
FileOutputStream fout = new FileOutputStream( "G:/to6.rar" );
byte [] buffer = new byte [BUFFER_SIZE];
while ( true ) {
int ins = fin.read(buffer);
if (ins == - 1 ) {
fin.close();
fout.flush();
fout.close();
break ;
} else {
fout.write(buffer, 0 , ins);
}
}
long endTime = System.currentTimeMillis();
System.out.println( "coypByStream time consumed(buffer size take effect) : " + (endTime - startTime));
}
}

• 测试结果

  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