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