JAVA NIO shorthand

(1)channel

filechannel(cannot used with sector as it's blocking) socketchannel serversocketchannel
datagramchannel(for udp)

serversocketchannel is responsible for monitoring tcp connection
main functions:
serersocketchannel open()
socketchannel accept() accept connection from client
sercersocket socket()
a sample:
ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();

serverSocketChannel.socket().bind(new InetSocketAddress(9999));
serverSocketChannel.configureBlocking(false);

while(true){
    SocketChannel socketChannel =
            serverSocketChannel.accept();

    if(socketChannel != null){
        //do something with socketChannel...
    }
}
socketchannel

(2)buffer

types:
    ByteBuffer
    MappedByteBuffer
    CharBuffer
    DoubleBuffer
    FloatBuffer
    IntBuffer
    LongBuffer
    ShortBuffer
perporties:
    capacity
    position
    limit
functions:
ByteBuffer buf = ByteBuffer.allocate(48);
int bytesRead = inChannel.read(buf); //read into buffer.
buf.put(127);
int bytesWritten = inChannel.write(buf);//read from buffer into channel.
byte aByte = buf.get();
flip()// change from read mode to write mode. set position to 0 and limit to previous position

a sample:
01    RandomAccessFile aFile = new RandomAccessFile("data/nio-data.txt", "rw");
02    FileChannel inChannel = aFile.getChannel();
03    
04    //create buffer with capacity of 48 bytes
05    ByteBuffer buf = ByteBuffer.allocate(48);
06    
07    int bytesRead = inChannel.read(buf); //read into buffer.
08    while (bytesRead != -1) {
09    
10      buf.flip();  //make buffer ready for read
11    
12      while(buf.hasRemaining()){
13          System.out.print((char) buf.get()); // read 1 byte at a time
14      }
15    
16      buf.clear(); //make buffer ready for writing
17      bytesRead = inChannel.read(buf);
18    }
19    aFile.close();

(3)sector

functions:

int select() // blocking until an event comes;

int select(long timeout)

int selectNow()

Set selectedKeys = selector.selectedKeys();

a sample:
Selector selector = Selector.open();  // get a slector
channel.configureBlocking(false); // set nonblocking
SelectionKey key = channel.register(selector, SelectionKey.OP_READ); // channel register to a slector with interesting events;
while(true) {
  int readyChannels = selector.select();  // blocking until an event comes;
  if(readyChannels == 0) continue;  // if no event changed, it will return 0;
  Set selectedKeys = selector.selectedKeys();
  Iterator keyIterator = selectedKeys.iterator();
  while(keyIterator.hasNext()) {
    SelectionKey key = keyIterator.next();
    if(key.isAcceptable()) {
        // a connection was accepted by a ServerSocketChannel.
    } else if (key.isConnectable()) {
        // a connection was established with a remote server.
    } else if (key.isReadable()) {
        // a channel is ready for reading
    } else if (key.isWritable()) {
        // a channel is ready for writing
    }
    keyIterator.remove();
  }
}