线程通信（二）

      在多线程中，会涉及到I/O相关的操作。这时会用到输入输出流：PipedOutputStream-PipedInputStream Pair 或者PipedWriter-PipedReader Pair。

    当Pipe处于空的状态时，read-thread会block，然后等待write-thread写入新内容；当Pipe处于写满的状态时，write-thread会block，然后等待read-thread读出内容。下面举个简单例子： 

public static void write(Writer rawOut) {
     try {
           BufferedWriter out = new BufferedWriter(rawOut);
           String[] line = {"this","is","a","thread","simple."};

           for (int i = 0; i < line.length; i++) {
                 if(i>0){out.write(" ");}   

                 out.write(line[i]);
           }
      }

      out.flush();
      out.close();
      } catch (IOException e) {
             e.printStackTrace();
      }
 }

public static void read(Reader rawIn) {
      try {
           BufferedReader in = new BufferedReader(rawIn);
           String line;

           while ((line = in.readLine()) != null) {
                System.out.println("read line: " + line);
           }
           System.out.println("read all data from pipe finished");
       } catch (IOException e) {
            e.printStackTrace();
       }
 }

 public static void main(String[] args) {
       try {
            final PipedWriter out = new PipedWriter();
            final PipedReader in = new PipedReader(out);

            Runnable ra = new Runnable() {
                   public void run() {
                          write(out);
                   }
            };
           Thread ta = new Thread(ra, "threadA");
           ta.start();

           Runnable rb = new Runnable() {
                  public void run() {
                         read(in);
                  }
            };
           Thread tb = new Thread(rb, "threadB");
           tb.start();

       } catch (IOException e) {
              e.printStackTrace();
       }
 }