其他高效拷贝文件方式Channel和MappedByteBuffer

Channel: 它是一个可以读写数据的通道,相当于IO流,但是与IO流有所不同,通道不区分输入和输出(是双向的)

channel的分类:

　　FileChannel 文件通道(用于读写文件)
　　SocketChannel TCP协议客户端通道
　　ServerSocketChannel TCP协议服务器通道

FileChannel类的基本使用

public class ByteBufferCopy {
    public static void main(String[] args) throws Exception {
        FileInputStream fileInputStream = new FileInputStream("111.txt");
        FileOutputStream fileOutputStream = new FileOutputStream("copt.txt");

        //获取ByteBuffer
        FileChannel ichannel = fileInputStream.getChannel();
        FileChannel ochannel = fileOutputStream.getChannel();
        //创建Channl
        ByteBuffer allocate = ByteBuffer.allocate(1024);
        int len = 0;
        while ((len = ichannel.read(allocate)) != -1) {
            allocate.flip();
            ochannel.write(allocate);
            allocate.clear();
        }
    }
}

FileChannel结合MappedByteBuffer实现高效读写

public class RandomAccessFiles {
    public static void main(String[] args) throws Exception {
        RandomAccessFile irandomAccessFile = new RandomAccessFile("111.txt", "r");
        RandomAccessFile orandomAccessFile = new RandomAccessFile("copt222.txt", "rw");
        FileChannel ichannel = irandomAccessFile.getChannel();
        FileChannel ochannel = orandomAccessFile.getChannel();
        //
        long size = ichannel.size();
        MappedByteBuffer inMap = ichannel.map(FileChannel.MapMode.READ_ONLY,0,size);
        MappedByteBuffer outMap = ochannel.map(FileChannel.MapMode.READ_WRITE, 0, size);
        //4.复制
        long start = System.currentTimeMillis();
        for (int i = 0; i < size; i++) {
            byte b = inMap.get(i);
            outMap.put(i,b);
        }
        long end = System.currentTimeMillis();
        System.out.println("耗时:" + (end - start));
    }
}