1

public class NioTest01 {
    public static void main(String[] args) {
        IntBuffer buffer = IntBuffer.allocate(10);

        for (int i = 0, j = buffer.capacity(); i < j; i++) {
            int random = new SecureRandom().nextInt(20);
            buffer.put(random);
        }

        buffer.flip();

        while (buffer.hasRemaining()) {
            System.out.println(buffer.get());
        }
    }
}

2

public class NioTest02 {
    public static void main(String[] args) throws Exception {
        FileInputStream fileInputStream = new FileInputStream("NioTest02.txt");
        FileChannel channel = fileInputStream.getChannel();

        ByteBuffer buffer = ByteBuffer.allocate(512);
        channel.read(buffer);

        buffer.flip();

        while (buffer.hasRemaining()) {
            byte b = buffer.get();
            System.out.printf("%c", b);
        }

        // 一定不要忘记
        fileInputStream.close();
    }
}

3

public class NioTest03 {
    public static void main(String[] args) throws Exception {
        FileOutputStream fileOutputStream = new FileOutputStream("nioTest03.txt");
        FileChannel fileChannel = fileOutputStream.getChannel();

        ByteBuffer byteBuffer = ByteBuffer.allocate(512);

        byte[] message = "hello world, welcome sumi~".getBytes();

        for (int i = 0; i < message.length; i++) {
            byteBuffer.put(message[i]);
        }

        byteBuffer.flip();

        fileChannel.write(byteBuffer);
        fileOutputStream.close();

    }
}

4

public class NioTest04 {
    public static void main(String[] args) throws Exception {
        FileInputStream inputStream = new FileInputStream("input.txt");
        FileOutputStream outputStream = new FileOutputStream("output.txt");
        FileChannel inputChannel = inputStream.getChannel();
        FileChannel outputChannel = outputStream.getChannel();

        ByteBuffer buffer = ByteBuffer.allocate(4);

        while (true) {
            //very very important 此代码注释掉，会造成死循环的写入
            buffer.clear();

            int read = inputChannel.read(buffer);
            System.out.println(read);
            if (read == -1) {
                break;
            }

            //important
            buffer.flip();

            outputChannel.write(buffer);
        }

        inputStream.close();
        outputStream.close();
    }
}

5

public class NioTest05 {
    public static void main(String[] args) {
        ByteBuffer buffer = ByteBuffer.allocate(64);

        buffer.putInt(20);
        buffer.putChar('韩');
        buffer.putLong(380380380L);
        buffer.putDouble(20.4d);
        buffer.put((byte) 13);
        buffer.putFloat(11.1f);
        buffer.putShort((short) 10);

        buffer.flip();
        System.out.println(buffer.getInt());
        System.out.println(buffer.getChar());
        System.out.println(buffer.getLong());
        System.out.println(buffer.getDouble());
        System.out.println(buffer.get());
        System.out.println(buffer.getFloat());
        System.out.println(buffer.getShort());
    }
}

6

/**
 * @author sm121
 * @date 2018/12/20.
 * slice 与原有的 buffer共享相同的底层数组
 * shift + esc 关闭Terminal窗口
 * tab键，用于更新后面的代码 buffer.position(2);  buffer.limit tab
 */
public class NioTest06 {
    public static void main(String[] args) {
        ByteBuffer buffer = ByteBuffer.allocate(10);

        for (int i = 0; i < buffer.capacity(); i++) {
            buffer.put((byte) i);
        }

        // [2,5)
        buffer.position(2);
        buffer.limit(5);

        ByteBuffer slice = buffer.slice();

        for (int i = 0; i < slice.capacity(); i++) {
            byte b = slice.get(i);
            b *= 2;
            slice.put(i, b);
        }

        buffer.position(0);
        buffer.limit(buffer.capacity());

        while (buffer.hasRemaining()) {
            System.out.println(buffer.get());
        }
    }
}

7

/**
 * @author sm121
 * @date 2018/12/20.
 * 普通buffer 可以转为 只读buffer，反过来不行。为什么
 */
public class NioTest07 {
    public static void main(String[] args) {
        ByteBuffer buffer = ByteBuffer.allocate(10);

        System.out.println(buffer.getClass());

        for (int i = 0; i < buffer.capacity(); i++) {
            buffer.put((byte) i);
        }

        ByteBuffer readOnlyBuffer = buffer.asReadOnlyBuffer();

        System.out.println(readOnlyBuffer.getClass());

        readOnlyBuffer.flip();

        while (readOnlyBuffer.hasRemaining()) {
            System.out.println(readOnlyBuffer.get());
        }
    }
}

8

public class NioTest08 {
    public static void main(String[] args) throws Exception {
        ByteBuffer buffer = ByteBuffer.allocateDirect(10);
    }
}

9

/**
 * @author sm121
 * @date 2018/12/21.
 * 内存映射文件，位于堆外内存
 */
public class NioTest09 {
    public static void main(String[] args) throws Exception {
        RandomAccessFile file = new RandomAccessFile("neicunyingshe.txt", "rw");

        FileChannel channel = file.getChannel();

        MappedByteBuffer map = channel.map(FileChannel.MapMode.READ_WRITE, 0, 10);
        map.putChar(0, 'c');
        map.putChar(2, 'z');

    }
}

10

public class NioTest10 {
    public static void main(String[] args) throws Exception {
        RandomAccessFile file = new RandomAccessFile("test.txt", "rw");
        FileChannel channel = file.getChannel();
        FileLock lock = channel.lock(0, 10, true);

        System.out.println("shared:" + lock.isShared());
        System.out.println("valid:" + lock.isValid());
    }
}

11

public class NioTest11 {
    public static void main(String[] args) throws Exception {
        int[] ports = new int[]{6666, 6667, 6668, 6669};

        Selector selector = Selector.open();

        for (int i = 0; i < ports.length; i++) {
            ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
            serverSocketChannel.configureBlocking(false);

            ServerSocket serverSocket = serverSocketChannel.socket();
            InetSocketAddress inetAddress = new InetSocketAddress(ports[i]);
            // bind
            serverSocket.bind(inetAddress);

            //register
            serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
            System.out.println("监听端口：" + ports[i]);
        }

        while (true) {
            int numbers = selector.select();
            System.out.println("numbers: " + numbers);

            Set<SelectionKey> selectionKeys = selector.selectedKeys();
            System.out.println("selected keys: " + selectionKeys);

            Iterator<SelectionKey> iterator = selectionKeys.iterator();

            while (iterator.hasNext()) {
                SelectionKey selectionKey = iterator.next();

                if (selectionKey.isAcceptable()) {
                    ServerSocketChannel serverSocketChannel = (ServerSocketChannel) selectionKey.channel();
                    SocketChannel socketChannel = serverSocketChannel.accept();
                    socketChannel.configureBlocking(false);

                    socketChannel.register(selector, SelectionKey.OP_READ);

                    //一定要注意移除
                    iterator.remove();
                    System.out.println("获得客户端连接：" + socketChannel);
                } else if (selectionKey.isReadable()) {
                    SocketChannel socketChannel = (SocketChannel) selectionKey.channel();

                    int bytesRead = 0;

                    while (true) {
                        ByteBuffer buffer = ByteBuffer.allocate(512);
                        buffer.clear();

                        int read = socketChannel.read(buffer);
                        if (read <= 0) {
                            break;
                        }
                        buffer.flip();
                        socketChannel.write(buffer);

                        bytesRead += read;
                    }
                    System.out.println("读取：" + bytesRead + "，来自于" + socketChannel);

                    //一定要注意移除
                    iterator.remove();
                }

            }

        }
    }
}