详解java NIO之Channel（通道）

 // 创建文件输出字节流
 FileOutputStream fos = new FileOutputStream("data.txt");
 //得到文件通道
 FileChannel fc = fos.getChannel();
 //往通道写入ByteBuffer
 fc.write(ByteBuffer.wrap("Some text ".getBytes()));
 //关闭流
 fos.close();

 //随机访问文件
 RandomAccessFile raf = new RandomAccessFile("data.txt", "rw");
 //得到文件通道
 fc = raf.getChannel();
 //设置通道的文件位置 为末尾
 fc.position(fc.size()); 
 //往通道写入ByteBuffer
 fc.write(ByteBuffer.wrap("Some more".getBytes()));
 //关闭
 raf.close();

 //创建文件输入流
 FileInputStream fs = new FileInputStream("data.txt");
 //得到文件通道
 fc = fs.getChannel();
 //分配ByteBuffer空间大小
 ByteBuffer buff = ByteBuffer.allocate(BSIZE);
 //从通道中读取ByteBuffer
 fc.read(buff);
 //调用此方法为一系列通道写入或相对获取 操作做好准备
 buff.flip();
 //从ByteBuffer从依次读取字节并打印
 while (buff.hasRemaining()){
  System.out.print((char) buff.get());
 }
 fs.close();

 SocketChannel sc = SocketChannel.open( );
 sc.connect (new InetSocketAddress ("somehost", someport)); 
 ServerSocketChannel ssc = ServerSocketChannel.open( ); 
 ssc.socket( ).bind (new InetSocketAddress (somelocalport)); 
 DatagramChannel dc = DatagramChannel.open( );

socketChannel.configureBlocking(false);
socketChannel.connect(new InetSocketAddress("http://jenkov.com", 80));

while(! socketChannel.finishConnect() ){
 //wait, or do something else...
}

 DatagramChannel channel = DatagramChannel.open( );
 DatagramSocket socket = channel.socket( ); 
 socket.bind (new InetSocketAddress (portNumber));

ByteBuffer header = ByteBuffer.allocateDirect (10); 
ByteBuffer body = ByteBuffer.allocateDirect (80); 
ByteBuffer [] buffers = { header, body }; 
int bytesRead = channel.read (buffers);

 ByteBuffer header = ByteBuffer.allocateDirect (10); 
 ByteBuffer body = ByteBuffer.allocateDirect (80); 
 ByteBuffer [] buffers = { header, body }; 
 channel.write(bufferArray);

public class GatheringTest {
 private static final String DEMOGRAPHIC = "output.txt";
 public static void main (String [] argv) throws Exception {
  int reps = 10;
  if (argv.length > 0) {
   reps = Integer.parseInt(argv[0]);
  }
  FileOutputStream fos = new FileOutputStream(DEMOGRAPHIC);
  GatheringByteChannel gatherChannel = fos.getChannel();

  ByteBuffer[] bs = utterBS(reps);

  while (gatherChannel.write(bs) > 0) {
   // 不做操作，让通道把数据输出到文件写完
  }
  System.out.println("Mindshare paradigms synergized to " + DEMOGRAPHIC);
  fos.close();
 }
 private static String [] col1 = { "Aggregate", "Enable", "Leverage",
          "Facilitate", "Synergize", "Repurpose",
          "Strategize", "Reinvent", "Harness"
         };

 private static String [] col2 = { "cross-platform", "best-of-breed", "frictionless",
          "ubiquitous", "extensible", "compelling",
          "mission-critical", "collaborative", "integrated"
         };

 private static String [] col3 = { "methodologies", "infomediaries", "platforms", "schemas", "mindshare", "paradigms", "functionalities", "web services", "infrastructures" };

 private static String newline = System.getProperty ("line.separator");


 private static ByteBuffer [] utterBS (int howMany) throws Exception {
  List list = new LinkedList();
  for (int i = 0; i < howMany; i++) {
   list.add(pickRandom(col1, " "));
   list.add(pickRandom(col2, " "));
   list.add(pickRandom(col3, newline));
  }
  ByteBuffer[] bufs = new ByteBuffer[list.size()];
  list.toArray(bufs);
  return (bufs);
 }
 private static Random rand = new Random( );


 /**
  * 随机生成字符
  * @param strings
  * @param suffix
  * @return
  * @throws Exception
  */
 private static ByteBuffer pickRandom (String [] strings, String suffix) throws Exception {
  String string = strings [rand.nextInt (strings.length)];
  int total = string.length() + suffix.length( );
  ByteBuffer buf = ByteBuffer.allocate (total);
  buf.put (string.getBytes ("US-ASCII"));
  buf.put (suffix.getBytes ("US-ASCII"));
  buf.flip( );
  return (buf);
 }
}

//通过Pipe.open()方法打开管道
Pipe pipe = Pipe.open();

//要向管道写数据，需要访问sink通道
Pipe.SinkChannel sinkChannel = pipe.sink();

//通过调用SinkChannel的write()方法，将数据写入SinkChannel
String newData = "New String to write to file..." + System.currentTimeMillis();
ByteBuffer buf = ByteBuffer.allocate(48);
buf.clear();
buf.put(newData.getBytes());
buf.flip();
while(buf.hasRemaining()) {
 sinkChannel.write(buf);
}

Pipe.SourceChannel sourceChannel = pipe.source();

ByteBuffer buf = ByteBuffer.allocate(48);
int bytesRead = sourceChannel.read(buf);