4种复制文件的方式性能比较
最近工作中涉及到了文件的下载，于是就想寻找一种最快的方式，考虑到在不考虑网络因素的情况下，下载和文件的复制其实可以理解为
一回事，本次测试中使用了4种方式

硬件如下
jdk 7

代码如下：
public class FileDownloader {

public static void copyFileUsingStream(File source, File dest) throws IOException {
    InputStream is = null;
    OutputStream os = null;
    try {
        is = new FileInputStream(source);
        os = new FileOutputStream(dest);
        byte[] buffer = new byte[1024];
        int length;
        while ((length = is.read(buffer)) > 0) {
            os.write(buffer, 0, length);
        }
    } finally {
        IOUtils.closeQuietly(is);
        IOUtils.closeQuietly(os);
    }
}

public static void copyFileUsingApacheCommonsIO(File source, File dest) throws IOException {
    FileUtils.copyFile(source, dest);
}

public static void copyFileUsingJava7Files(File source, File dest) throws IOException {
    Files.copy(source.toPath(), dest.toPath());
}

public static void copyFileUsingChannel(File source, File dest) throws IOException {
    FileChannel sourceChannel = null;
    FileChannel destChannel = null;
    try {
        sourceChannel = new FileInputStream(source).getChannel();
        destChannel = new FileOutputStream(dest).getChannel();
        destChannel.transferFrom(sourceChannel, 0, Long.MAX_VALUE);
    } finally {
        IOUtils.closeQuietly(sourceChannel);
        IOUtils.closeQuietly(destChannel);
    }
}

}
测试代码如下：

public class FileDownloaderTest {

private File source;

private File dest;

@Test
public void testCopyFileUsingStream() throws Exception {
    source = new File("e://1.avi");
    dest = new File("d://1.avi");

    long start = System.nanoTime();
    FileDownloader.copyFileUsingStream(source, dest);
    System.out.println("Time taken by Stream Copy = " + (System.nanoTime() - start));
}

@Test
public void testCopyFileUsingApacheCommonsIO() throws Exception {
    source = new File("e://2.avi");
    dest = new File("d://2.avi");
    long start = System.nanoTime();
    FileDownloader.copyFileUsingApacheCommonsIO(source, dest);
    System.out.println("Time taken by Apache Commons IO Copy = " + (System.nanoTime() - start));
}

@Test
public void testCopyFileUsingJava7Files() throws Exception {
    source = new File("e://3.avi");
    dest = new File("d://3.avi");
    long start = System.nanoTime();
    FileDownloader.copyFileUsingJava7Files(source, dest);
    System.out.println("Time taken by Java7 Files Copy = " + (System.nanoTime() - start));
}

@Test
public void testCopyFileUsingChannel() throws Exception {
    source = new File("e://4.avi");
    dest = new File("d://4.avi");
    long start = System.nanoTime();
    FileDownloader.copyFileUsingChannel(source, dest);
    System.out.println("Time taken by Channel Copy = " + (System.nanoTime() - start));
}

}
测试方法：

将同样的文件，在原始目录下，复制4份，文件名不同，文件一摸一样。然后多次执行测试代码。

做了2组测试，每组执行了3次，结果如下：

文件大小：98.3M

Time taken by Apache Commons IO Copy = 64954135
Time taken by Stream Copy = 375539829
Time taken by Channel Copy = 57012898
Time taken by Java7 Files Copy = 65101591

Time taken by Apache Commons IO Copy = 63818085
Time taken by Stream Copy = 375973711
Time taken by Channel Copy = 57417522
Time taken by Java7 Files Copy = 65688487

Time taken by Apache Commons IO Copy = 63172674
Time taken by Stream Copy = 354136258
Time taken by Channel Copy = 58497984
Time taken by Java7 Files Copy = 79916185

文件大小：746M

Time taken by Apache Commons IO Copy = 660830180
Time taken by Stream Copy = 2791359285
Time taken by Channel Copy = 3861113037
Time taken by Java7 Files Copy = 6162249000

Time taken by Apache Commons IO Copy = 381343255
Time taken by Channel Copy = 2987676936
Time taken by Stream Copy = 2856878081
Time taken by Java7 Files Copy = 19034765260

Time taken by Apache Commons IO Copy = 419664709
Time taken by Stream Copy = 2761465029
Time taken by Channel Copy = 4183763748
Time taken by Java7 Files Copy = 23261100925
结论 nio 方式比较快

==============================================================================本文转自被遗忘的博客园博客，原文链接：http://www.cnblogs.com/rollenholt/p/4227558.html，如需转载请自行联系原作者