（二）JAVA NIO CHANNEL

FileChannel 从文件中读写数据。

FileChannelTest.java

public class FileChannelTest {

    public static void main(String[] args) throws IOException {
        FileChannel inputFileChannel = new FileInputStream("file.text absolute path").getChannel();
        ByteBuffer readBuffer = ByteBuffer.allocate(100);
        inputFileChannel.read(readBuffer);
        readBuffer.flip();
        for (int i = 0; i < readBuffer.limit(); i++) {
            System.out.println((char) readBuffer.get());
        }

        FileChannel outputFileChannel = new FileOutputStream("file.text absolute path", true).getChannel();
        ByteBuffer writeBuffer = ByteBuffer.wrap("TOM".getBytes());
        outputFileChannel.write(writeBuffer);

        inputFileChannel.close();
        outputFileChannel.close();
    }
}

DatagramChannel 能通过UDP读写网络中的数据。

DatagramChannelServer.java

public class DatagramChannelServer {
    public static void main(String[] args) throws IOException {
        DatagramChannel channel = DatagramChannel.open();
        channel.socket().bind(new InetSocketAddress(9999));

        ByteBuffer buf = ByteBuffer.allocate(48);
        while (true) {
            channel.receive(buf);
            buf.flip();
            for (int i = 0; i < buf.limit(); i++) {
                System.out.println((char) buf.get());
            }
            buf.clear();
        }
    }
}

DatagramChannelClient.java

public class DatagramChannelClient {
    public static void main(String[] args) throws IOException {
        DatagramChannel channel = DatagramChannel.open();
        ByteBuffer buf = ByteBuffer.allocate(48);
        buf = buf.wrap("AA".getBytes());
        channel.send(buf, new InetSocketAddress("localhost", 9999));
    }
}

ServerSocketChannel 可以监听新进来的TCP连接，像Web服务器那样。对每一个新进来的连接都会创建一个SocketChannel。

SocketChannel 能通过TCP读写网络中的数据。

NioChannelServer.java

public class NioChannelServer {
    public static void main(String[] args) throws IOException {
        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
        serverSocketChannel.socket().bind(new InetSocketAddress(9999));
        ByteBuffer buf = ByteBuffer.allocate(48);
        while (true) {
            SocketChannel channel = serverSocketChannel.accept();
            while (true) {
                channel.read(buf);
                buf.flip();
                for (int i = 0; i < buf.limit(); i++) {
                    System.out.println((char) buf.get());
                }
                buf.clear();
            }
        }
    }
}

NioChannelClient.java

public class NioChannelClient {
    public static void main(String[] args) throws IOException {
        SocketChannel socketChannel = SocketChannel.open();
        socketChannel.connect(new InetSocketAddress("localhost", 9999));
        while (true) {
            Scanner input = new Scanner(System.in);
            socketChannel.write(ByteBuffer.wrap(input.nextLine().getBytes()));
        }
    }
}

Nio源码地址​github.com