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

 

1. package com;   
2.   
3. import java.io.File;   
4. import java.io.FileInputStream;   
5. import java.io.FileOutputStream;   
6. import java.io.IOException;   
7. import java.nio.ByteBuffer;   
8. import java.nio.channels.FileChannel;   
9.   
10. import junit.framework.TestCase;   
11.   
12. /**  
13.  * NIO read write test  
14.  *   
15.  * @author wutao  
16.  *   
17.  */  
18. public class NioDemo extends TestCase {   
19.   
20.     public void testRead() throws IOException {   
21.   
22.         int[] sizes = { 10000, 1000, 100, 50, 5, 1 };   
23.   
24.         // Arrays.sort(sizes);   
25.   
26.         System.out.println(new File("text.txt").length());   
27.   
28.         for (int i = 0; i < sizes.length; i++) {   
29.   
30.             int size = sizes[i];   
31.   
32.             FileInputStream fins = new FileInputStream("text.txt");   
33.   
34.             FileChannel fc = fins.getChannel();   
35.   
36.             if (!new File("text2.txt").exists()) {   
37.                 new File("text2.txt").createNewFile();   
38.             }   
39.             ByteBuffer buffer = ByteBuffer.allocate(size);   
40.   
41.             FileOutputStream fouts = new FileOutputStream("text2.txt");   
42.             FileChannel fc2 = fouts.getChannel();   
43.   
44.             long start = System.currentTimeMillis();   
45.   
46.             while (true) {   
47.                 buffer.clear();   
48.                 int r = fc.read(buffer);   
49.                 if (r == -1) {   
50.                     break;   
51.                 }   
52.                 buffer.flip();   
53.                 fc2.write(buffer);   
54.             }   
55.   
56.             long end = System.currentTimeMillis();   
57.   
58.             System.out.println("---------" + size + "---------");   
59.             System.out.println(end - start);   
60.             fc.close();   
61.             fc2.close();   
62.             fins.close();   
63.             fouts.close();   
64.         }   
65.     }   
66. }   

 

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

 

1. import java.io.*;   
2. import java.nio.*;   
3. import java.nio.channels.*;   
4. public class NIOCopier {   
5.   public static void main(String[] args) throws IOException {   
6.     FileInputStream inFile = new FileInputStream(args[0]);   
7.     FileOutputStream outFile = new FileOutputStream(args[1]);   
8.     FileChannel inChannel = inFile.getChannel( );   
9.     FileChannel outChannel = outFile.getChannel( );   
10.     for (ByteBuffer buffer = ByteBuffer.allocate(1024*1024);   
11.     inChannel.read(buffer) != -1;   
12.     buffer.clear( )) {   
13.       buffer.flip( );   
14.       while (buffer.hasRemaining( )) outChannel.write(buffer);   
15.     }   
16.     inChannel.close( );   
17.     outChannel.close( );   
18.   }   
19. }   
20.   

 

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.