JavaNIO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

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