java-nio

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NIO.

Java non-blocking IO (NIO)

  • Support form JDK 1.4
  • java.nio.buffer
    capacity
    limit
    position
    mark

  • Allocate buffer

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    ByteBuffer buf = ByteBuffer.allocate(20);       // allocate in heap.
    ByteBuffer buf = ByteBuffer.allocateDirect(20;) // allocate in off-heap.

  • ByteBuffer common operations

    • rewind() : pos=0, mark discard
    • clear() : pos=0, lim=cap, mark discard
    • flip() : lim=pos, pos=0, mark discard
    • reset() : pos=mark
    • slice() : split a buffer at remaining position

Garbage Collection (GC)

System.gc()

Channel

  1. FileChannel
    Copy file by Channel.

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    public void copyFile() {
        try {
            FileInputStream fis = new FileInputStream("TestChannelSrc.txt");
            FileChannel fcin = fis.getChannel();
            FileOutputStream fos = new FileOutputStream("TestChannelDst.txt");
            FileChannel fcout = fos.getChannel();
            ByteBuffer buf = ByteBuffer.allocate(1024 * 50);
            while(fcin.read(buf) != -1) {
                buf.flip();
                fcout.write(buf);
                buf.clear();
            }
            fis.close();
            fos.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
        
    }

  2. SocketChannel
    SocketChannelImage
    Full code can be found on github.

  3. MappedByteBuffer
    Map File on device to memory synchronizely.
    Full code can be found on github.