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Language: Java
Expertise: Beginner

Jun 1, 1999

Piped streams are typically used in separate threads. One thread writes output to a PipedOutputStream. The other thread reads the same data from a PipedInputStream. The two streams are connected either through their constructors or through an explicit connect() method. To find out how to instantiate piped streams, see the tips "Connecting the Piped Stream Classes" and "Using Piped Streams in an Application."

You can use the piped streams in two dependent threads in a single class. This class creates two piped streams and connects them through the constructor in Lines 1-2. Lines 4-5 construct two threads with these streams as a parameter to each of them. The thread inThread will read in the data from the pins and the thread outThread will write the data to pouts. Lines 7-8 start the threads.

 
1.      private PipedInputStream pins = new PipedInputStream();
2.      private PipedOutputStream pouts = new PipedOutputStream(pins);
3.
4.    Thread inThread = new PipedInputThread(pins);
5.    Thread outThread = new PipedOutputThread(pouts);
6.
7.    inThread.start();
8.    outThread.start();

The code for the run() methods for the two threads is given in the tip "Running Piped Threads." However, the classes are defined here. The class PipedInputThread is as follows:

 
1. class PipedInputThread extends Thread {
2.   InputStream in_ = null;
3.
4.   public PipedInputThread (InputStream in) { in_ = in; }
5.   public void run () {
6.     // Code that reads in from the PipedInputStream "in_"
7.   }
8. }

The code for the class PipedOutputThread is similar:

 
1. class PipedOutputThread extends Thread {
2.      OutputStream out_ = null;
3.
4.      public PipedOutputThread (OutputStream out) { out_ = out; }
5.      public void run ()
6.        // Code that writes out to the PipedOutputStream "out_"
7.      }
8. }