高效的文件拷贝之MappedByteBuffer

我们经常对文件进行操作，但是效率却一般。最近在研究MappedByteBuffer的用法，下面是例子：

void MappedByteBufferTest() {
    try {
        RandomAccessFile source = new RandomAccessFile("F:\\cmb-flume\\flume\\logs\\relog\\paas0.log", "r");
        RandomAccessFile target = new RandomAccessFile("F:\\cmb-flume\\flume\\logs\\relog\\1.log", "rw");
        FileChannel in = source.getChannel();
        FileChannel out = target.getChannel();
        long size = in.size();
        MappedByteBuffer mbbi = in.map(FileChannel.MapMode.READ_ONLY, 0, size);
        MappedByteBuffer mbbo = out.map(FileChannel.MapMode.READ_WRITE, 0, size);
        long start = System.currentTimeMillis();
        for (int i = 0; i < size; i++) {
            byte b = mbbi.get(i);
            mbbo.put(i, b);
        }
        source.close();
        target.close();
        System.out.println("Spend: " + (System.currentTimeMillis() - start) + "ms");
    } catch (Exception e) {
        // TODO: handle exception
    }
}

打印：Spend: 170ms

paas0.log的大小是197M，耗时170毫秒，换算一下1毫秒可以读取1.15M。1秒钟的话可以读取1.13G大小的文件。