Java NIO性能测试

java 代码：

package com;      
     
import java.io.File;      
import java.io.FileInputStream;      
import java.io.FileOutputStream;      
import java.io.IOException;      
import java.nio.ByteBuffer;      
import java.nio.channels.FileChannel;      
     
import junit.framework.TestCase;      
     
/**     
 * NIO read write test     
 *      
 * @author wutao     
 *      
 */     
public class NioDemo extends TestCase {      
     
    public void testRead() throws IOException {      
     
        int[] sizes = { 10000, 1000, 100, 50, 5, 1 };      
     
        // Arrays.sort(sizes);      
     
        System.out.println(new File("text.txt").length());      
     
        for (int i = 0; i < sizes.length; i++) {      
     
            int size = sizes[i];      
     
            FileInputStream fins = new FileInputStream("text.txt");      
     
            FileChannel fc = fins.getChannel();      
     
            if (!new File("text2.txt").exists()) {      
                new File("text2.txt").createNewFile();      
            }      
            ByteBuffer buffer = ByteBuffer.allocate(size);      
     
            FileOutputStream fouts = new FileOutputStream("text2.txt");      
            FileChannel fc2 = fouts.getChannel();      
     
            long start = System.currentTimeMillis();      
     
            while (true) {      
                buffer.clear();      
                int r = fc.read(buffer);      
                if (r == -1) {      
                    break;      
                }      
                buffer.flip();      
                fc2.write(buffer);      
            }      
     
            long end = System.currentTimeMillis();      
     
            System.out.println("---------" + size + "---------");      
            System.out.println(end - start);      
            fc.close();      
            fc2.close();      
            fins.close();      
            fouts.close();      
        }      
    }      
}     

Java™ I/O, 2nd Edition  
By Elliotte Rusty Harold   
...............................................   
Publisher: O'Reilly   
Pub Date: May 2006   
Print ISBN-10: 0-596-52750-0   
Print ISBN-13: 978-0-59-652750-1   
Pages: 726  

import java.io.*;     
import java.nio.*;     
import java.nio.channels.*;     
public class NIOCopier {     
  public static void main(String[] args) throws IOException {     
    FileInputStream inFile = new FileInputStream(args[0]);     
    FileOutputStream outFile = new FileOutputStream(args[1]);     
    FileChannel inChannel = inFile.getChannel( );     
    FileChannel outChannel = outFile.getChannel( );     
    for (ByteBuffer buffer = ByteBuffer.allocate(1024*1024);     
    inChannel.read(buffer) != -1;     
    buffer.clear( )) {     
      buffer.flip( );     
      while (buffer.hasRemaining( )) outChannel.write(buffer);     
    }     
    inChannel.close( );     
    outChannel.close( );     
  }     
}     

In a very unscientific test, copying one large (4.3-GB) file on one platform (a dual 2.5-GHz PowerMac G5 running Mac OS X 10.4.1) using traditional I/O with buffered streams and an 8192-byte buffer took 305 seconds. Expanding and reducing the buffer size didn't shift the overall numbers more than 5% and if anything tended to increase the time to copy. (Using a one-megabyte buffer like Example 14-1's actually increased the time to over 23 minutes.) Using new I/O as implemented in Example 14-1 was about 16% faster, at 255 seconds. A straight Finder copy took 197 seconds. Using the Unix cp command actually took 312 seconds, so the Finder is doing some surprising optimizations under the hood.

原文链接：http://wutaoo.iteye.com/blog/94666