测试NIO性能

时间(ms)	文件大小(byte)
Buffer(byte)	434	603900
10000	0	0
1000	0	46
100	0	188
50	0	281
5	0	2406
1	47	12000

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

java 代码

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.