檔案的複製最能體現io效率了.因為既需要讀取資料還需要寫出到硬碟中,下面提供了三種檔案複製的方法 可以對比一下 直接緩衝區與非直接緩衝區的效率對比.

public class Nio {

    public static void main(String[] args) throws IOException {
        nioCopyTest1();
        nioCopyTest2();
        nioCopyTest3();
    }

    /**通道之間的資料傳輸(直接緩衝區的模式)
     *
     */
private static void   nioCopyTest3() throws 
 
IOException {
        long startTime = System.currentTimeMillis();

        FileChannel inChannel = FileChannel.open(Paths.get("E:\\ 1.avi"), StandardOpenOption.READ);

        FileChannel outChennel = FileChannel.open(Paths.get("E:\\ 13.avi"),StandardOpenOption.WRITE,StandardOpenOption.READ,StandardOpenOption.CREATE_NEW
 
);

        outChennel.transferFrom(inChannel,0,inChannel.size());

        long end = System.currentTimeMillis();
        System.out.println("nioCopyTest3耗費時間:"+(end-startTime));
    }

    /**
     * 使用直接緩衝區完成檔案的複製(記憶體對映檔案)
     */
private static void  nioCopyTest2() throws IOException {
        long 
 
startTime = System.currentTimeMillis();

        FileChannel inChannel = FileChannel.open(Paths.get("E:\\ 1.avi"), StandardOpenOption.READ);

        FileChannel outChennel = FileChannel.open(Paths.get("E:\\ 12.avi"),StandardOpenOption.WRITE,StandardOpenOption.READ,StandardOpenOption.CREATE_NEW);

        //記憶體對映檔案(什麼模式 從哪開始 到哪結束)
MappedByteBuffer inMappeBuf = inChannel.map(FileChannel.MapMode.READ_ONLY,0,inChannel.size());
        MappedByteBuffer outMappeBuf =  outChennel.map(FileChannel.MapMode.READ_WRITE,0,inChannel.size());

        //直接都緩衝區進行資料的讀寫操作
byte[] dst = new byte[inMappeBuf.limit()];
        inMappeBuf.get(dst);
        outMappeBuf.put(dst);

        inChannel.close();
        outChennel.close();
        long end = System.currentTimeMillis();
        System.out.println("nioCopyTest2耗費時間:"+(end-startTime));
    }


    /**
     *  非直接緩衝區 檔案的複製
* @throws IOException
     */
private static void nioCopyTest1()throws IOException {
        long startTime = System.currentTimeMillis();
        FileInputStream fileInputStream = new FileInputStream(new File("E:\\ 1.avi"));
        FileOutputStream fileOutputStream = new FileOutputStream("E:\\ 11.avi");

        //獲取通道
FileChannel inChannel = fileInputStream.getChannel();
        FileChannel outChanel = fileOutputStream.getChannel();

        //分配緩衝區的大小
ByteBuffer buf = ByteBuffer.allocate(1024);

        //將通道中的資料存入緩衝區
while (inChannel.read(buf) != -1) {
            buf.flip();//切換讀取資料的模式
outChanel.write(buf);
            buf.clear();
        }
        outChanel.close();
        inChannel.close();
        fileInputStream.close();
        fileOutputStream.close();
        long end = System.currentTimeMillis();
        System.out.println("nioCopyTest1耗費時間:"+(end-startTime));
    }
}

控制檯輸出:

nioCopyTest1耗費時間:1417
nioCopyTest2耗費時間:142

nioCopyTest3耗費時間:68

直接緩衝不需要檔案的複製拷貝 所以大大增加效率 其中第三種方法通道之間的檔案傳輸 速度最快了直接在通道中完成.