Example usage for java.nio ByteBuffer allocate

List of usage examples for java.nio ByteBuffer allocate

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Introduction

In this page you can find the example usage for java.nio ByteBuffer allocate.

Prototype

public static ByteBuffer allocate(int capacity)

Source Link

Document

Creates a byte buffer based on a newly allocated byte array.

Usage

From source file:MainClass.java

public static void main(String[] args) {

    String phrase = new String("www.java2s.com API \n");
    File aFile = new File("test.txt");

    FileOutputStream file = null;
    try {//  ww  w  .  ja v  a 2 s .co m
        file = new FileOutputStream(aFile, true);
    } catch (FileNotFoundException e) {
        e.printStackTrace(System.err);
    }
    FileChannel outChannel = file.getChannel();
    ByteBuffer buf = ByteBuffer.allocate(phrase.length());
    byte[] bytes = phrase.getBytes();
    buf.put(bytes);
    buf.flip();

    try {
        outChannel.write(buf);
        file.close();
    } catch (IOException e) {
        e.printStackTrace(System.err);
    }
}

From source file:UDPTimeClient.java

public static void main(String[] args) throws Exception {

    DatagramChannel channel = DatagramChannel.open();
    // port 0 selects any available port
    SocketAddress address = new InetSocketAddress(0);
    DatagramSocket socket = channel.socket();
    socket.setSoTimeout(5000);/*from w  w  w  .ja  v a2s .c o m*/
    socket.bind(address);

    SocketAddress server = new InetSocketAddress("time.nist.gov", 37);
    ByteBuffer buffer = ByteBuffer.allocate(8192);
    // time protocol always uses big-endian order
    buffer.order(ByteOrder.BIG_ENDIAN);
    // Must put at least one byte of data in the buffer;
    // it doesn't matter what it is.
    buffer.put((byte) 65);
    buffer.flip();

    channel.send(buffer, server);

    buffer.clear();
    buffer.put((byte) 0).put((byte) 0).put((byte) 0).put((byte) 0);
    channel.receive(buffer);
    buffer.flip();
    long secondsSince1970 = buffer.getLong();

    System.out.println(secondsSince1970);
    channel.close();

}

From source file:MainClass.java

public static void main(String[] args) throws IOException {

    DatagramChannel channel = DatagramChannel.open();
    SocketAddress address = new InetSocketAddress(0);
    DatagramSocket socket = channel.socket();
    socket.bind(address);//from w ww .j  a  v a 2 s.  c  o  m

    SocketAddress server = new InetSocketAddress("time-a.nist.gov", 37);
    channel.connect(server);

    ByteBuffer buffer = ByteBuffer.allocate(8);
    buffer.order(ByteOrder.BIG_ENDIAN);
    // send a byte of data to the server
    buffer.put((byte) 0);
    buffer.flip();
    channel.write(buffer);

    // get the buffer ready to receive data
    buffer.clear();
    // fill the first four bytes with zeros
    buffer.putInt(0);
    channel.read(buffer);
    buffer.flip();

    // convert seconds since 1900 to a java.util.Date
    long secondsSince1900 = buffer.getLong();
    long differenceBetweenEpochs = 2208988800L;
    long secondsSince1970 = secondsSince1900 - differenceBetweenEpochs;
    long msSince1970 = secondsSince1970 * 1000;
    Date time = new Date(msSince1970);

    System.out.println(time);
}

From source file:MainClass.java

public static void main(String[] args) {
    File aFile = new File("data.dat");
    FileInputStream inFile = null;

    try {/* w w  w .ja  va 2  s  . c  o  m*/
        inFile = new FileInputStream(aFile);
    } catch (FileNotFoundException e) {
        e.printStackTrace(System.err);
        System.exit(1);
    }

    FileChannel inChannel = inFile.getChannel();
    final int COUNT = 6;
    ByteBuffer buf = ByteBuffer.allocate(8 * COUNT);
    long[] data = new long[COUNT];
    try {
        int pos = 0;
        while (inChannel.read(buf) != -1) {
            try {
                ((ByteBuffer) (buf.flip())).asLongBuffer().get(data);
                pos = data.length;
            } catch (BufferUnderflowException e) {
                LongBuffer longBuf = buf.asLongBuffer();
                pos = longBuf.remaining();
                longBuf.get(data, 0, pos);
            }
            System.out.println();
            for (int i = 0; i < pos; i++) {
                System.out.printf("%10d", data[i]);
            }
            buf.clear();
        }
        System.out.println("\nEOF reached.");
        inFile.close();
    } catch (IOException e) {
        e.printStackTrace(System.err);
        System.exit(1);
    }
}

From source file:MainClass.java

public static void main(String[] args) throws IOException {
    Charset charset = Charset.forName("ISO-8859-1");
    CharsetEncoder encoder = charset.newEncoder();
    CharsetDecoder decoder = charset.newDecoder();

    ByteBuffer buffer = ByteBuffer.allocate(512);

    Selector selector = Selector.open();

    ServerSocketChannel server = ServerSocketChannel.open();
    server.socket().bind(new java.net.InetSocketAddress(8000));
    server.configureBlocking(false);//w  ww.jav  a  2  s. com
    SelectionKey serverkey = server.register(selector, SelectionKey.OP_ACCEPT);

    for (;;) {
        selector.select();
        Set keys = selector.selectedKeys();

        for (Iterator i = keys.iterator(); i.hasNext();) {
            SelectionKey key = (SelectionKey) i.next();
            i.remove();

            if (key == serverkey) {
                if (key.isAcceptable()) {
                    SocketChannel client = server.accept();
                    client.configureBlocking(false);
                    SelectionKey clientkey = client.register(selector, SelectionKey.OP_READ);
                    clientkey.attach(new Integer(0));
                }
            } else {
                SocketChannel client = (SocketChannel) key.channel();
                if (!key.isReadable())
                    continue;
                int bytesread = client.read(buffer);
                if (bytesread == -1) {
                    key.cancel();
                    client.close();
                    continue;
                }
                buffer.flip();
                String request = decoder.decode(buffer).toString();
                buffer.clear();
                if (request.trim().equals("quit")) {
                    client.write(encoder.encode(CharBuffer.wrap("Bye.")));
                    key.cancel();
                    client.close();
                } else {
                    int num = ((Integer) key.attachment()).intValue();
                    String response = num + ": " + request.toUpperCase();
                    client.write(encoder.encode(CharBuffer.wrap(response)));
                    key.attach(new Integer(num + 1));
                }
            }
        }
    }
}

From source file:MainClass.java

public static void main(String[] args) {
    long[] primes = new long[] { 1, 2, 3, 5, 7 };
    File aFile = new File("C:/test/primes.bin");
    FileOutputStream outputFile = null;
    try {//w  ww .  ja  v  a  2 s  .com
        outputFile = new FileOutputStream(aFile);
    } catch (FileNotFoundException e) {
        e.printStackTrace(System.err);
    }
    FileChannel file = outputFile.getChannel();
    final int BUFFERSIZE = 100;
    ByteBuffer buf = ByteBuffer.allocate(BUFFERSIZE);
    LongBuffer longBuf = buf.asLongBuffer();
    int primesWritten = 0;
    while (primesWritten < primes.length) {
        longBuf.put(primes, primesWritten, min(longBuf.capacity(), primes.length - primesWritten));
        buf.limit(8 * longBuf.position());
        try {
            file.write(buf);
            primesWritten += longBuf.position();
        } catch (IOException e) {
            e.printStackTrace(System.err);
        }
        longBuf.clear();
        buf.clear();
    }
    try {
        System.out.println("File written is " + file.size() + "bytes.");
        outputFile.close();
    } catch (IOException e) {
        e.printStackTrace(System.err);
    }
}

From source file:MainClass.java

public static void main(String[] args) {
    String phrase = new String("text\n");
    String dirname = "C:/test"; // Directory name
    String filename = "byteData.txt";
    File aFile = new File(dirname, filename);
    // Create the file output stream
    FileOutputStream file = null;
    try {//  w  w w  .  j a  v a 2  s  .  c o  m
        file = new FileOutputStream(aFile, true);
    } catch (FileNotFoundException e) {
        e.printStackTrace(System.err);
    }
    FileChannel outChannel = file.getChannel();
    ByteBuffer buf = ByteBuffer.allocate(phrase.length());
    byte[] bytes = phrase.getBytes();
    buf.put(bytes);
    buf.flip();
    try {
        outChannel.write(buf);
        file.close();
    } catch (IOException e) {
        e.printStackTrace(System.err);
    }
}

From source file:BufferToText.java

public static void main(String[] args) throws Exception {
    FileChannel fc = new FileOutputStream("data2.txt").getChannel();
    fc.write(ByteBuffer.wrap("Some text".getBytes()));
    fc.close();//w  w w.  j  av a2s .c o  m
    fc = new FileInputStream("data2.txt").getChannel();
    ByteBuffer buff = ByteBuffer.allocate(BSIZE);
    fc.read(buff);
    buff.flip();
    // Doesn't work:
    System.out.println(buff.asCharBuffer());
    // Decode using this system's default Charset:
    buff.rewind();
    String encoding = System.getProperty("file.encoding");
    System.out.println("Decoded using " + encoding + ": " + Charset.forName(encoding).decode(buff));
    // Or, we could encode with something that will print:
    fc = new FileOutputStream("data2.txt").getChannel();
    fc.write(ByteBuffer.wrap("Some text".getBytes("UTF-16BE")));
    fc.close();
    // Now try reading again:
    fc = new FileInputStream("data2.txt").getChannel();
    buff.clear();
    fc.read(buff);
    buff.flip();
    System.out.println(buff.asCharBuffer());
    // Use a CharBuffer to write through:
    fc = new FileOutputStream("data2.txt").getChannel();
    buff = ByteBuffer.allocate(24); // More than needed
    buff.asCharBuffer().put("Some text");
    fc.write(buff);
    fc.close();
    // Read and display:
    fc = new FileInputStream("data2.txt").getChannel();
    buff.clear();
    fc.read(buff);
    buff.flip();
    System.out.println(buff.asCharBuffer());
}

From source file:ChannelCopy.java

public static void main(String[] args) throws Exception {
    if (args.length != 2) {
        System.out.println("arguments: sourcefile destfile");
        System.exit(1);//from   ww  w. j a v  a 2s.  com
    }
    FileChannel in = new FileInputStream(args[0]).getChannel(),
            out = new FileOutputStream(args[1]).getChannel();
    ByteBuffer buffer = ByteBuffer.allocate(BSIZE);
    while (in.read(buffer) != -1) {
        buffer.flip(); // Prepare for writing
        out.write(buffer);
        buffer.clear(); // Prepare for reading
    }
}

From source file:MainClass.java

public static void main(String[] args) {
    long[] primes = new long[] { 1, 2, 3, 5, 7 };
    File aFile = new File("C:/test/primes.txt");
    FileOutputStream outputFile = null;
    try {//from   w w  w .j  a  va  2 s  .c  o  m
        outputFile = new FileOutputStream(aFile);
    } catch (FileNotFoundException e) {
        e.printStackTrace(System.err);
    }
    FileChannel file = outputFile.getChannel();
    final int BUFFERSIZE = 100;
    ByteBuffer buf = ByteBuffer.allocate(BUFFERSIZE);
    DoubleBuffer doubleBuf = buf.asDoubleBuffer();
    buf.position(8);
    CharBuffer charBuf = buf.asCharBuffer();
    for (long prime : primes) {
        String primeStr = "prime = " + prime;
        doubleBuf.put(0, (double) primeStr.length());
        charBuf.put(primeStr);
        buf.position(2 * charBuf.position() + 8);
        LongBuffer longBuf = buf.asLongBuffer();
        longBuf.put(prime);
        buf.position(buf.position() + 8);
        buf.flip();
        try {
            file.write(buf);
        } catch (IOException e) {
            e.printStackTrace(System.err);
        }
        buf.clear();
        doubleBuf.clear();
        charBuf.clear();
    }
    try {
        System.out.println("File written is " + file.size() + "bytes.");
        outputFile.close();
    } catch (IOException e) {
        e.printStackTrace(System.err);
    }
}