NIO

	RandomAccessFile aFile = new RandomAccessFile("data/nio-data.txt", "rw");
	FileChannel inChannel = aFile.getChannel();
	ByteBuffer buf = ByteBuffer.allocate(48);
	int bytesRead = inChannel.read(buf);
	while (bytesRead != -1) {
		System.out.println("Read " + bytesRead);
		//首先读取数据的Buffer，然后反转Buffer，再从Buffer中读取数据
		buf.flip();
		while(buf.hasRemaining()){
			System.out.print((char) buf.get());
		}
		buf.clear();
		bytesRead = inChannel.read(buf);
	}
	aFile.close();