Java Doc for Rendezvous.java in  » Ajax » Laszlo-4.0.10 » EDU » oswego » cs » dl » util » concurrent » Java Source Code / Java DocumentationJava Source Code and Java Documentation

• Unlike a CyclicBarrier, is not restricted to use with fixed-sized groups of threads. Any number of threads can attempt to enter a rendezvous, but only the predetermined number of parties enter and later become released from the rendezvous at any give time.
• Enables each participating thread to exchange information with others at the rendezvous point. Each entering thread presents some object on entry to the rendezvous, and returns some object on release. The object returned is the result of a RendezvousFunction that is run once per rendezvous, (it is run by the last-entering thread). By default, the function applied is a rotation, so each thread returns the object given by the next (modulo parties) entering thread. This default function faciliates simple application of a common use of rendezvous, as exchangers.

Rendezvous use an all-or-none breakage model for failed synchronization attempts: If threads leave a rendezvous point prematurely because of timeout or interruption, others will also leave abnormally (via BrokenBarrierException), until the rendezvous is restarted. This is usually the simplest and best strategy for sharing knowledge about failures among cooperating threads in the most common usages contexts of Rendezvous.

While any positive number (including 1) of parties can be handled, the most common case is to have two parties.

Sample Usage

Here are the highlights of a class that uses a Rendezvous to swap buffers between threads so that the thread filling the buffer gets a freshly emptied one when it needs it, handing off the filled one to the thread emptying the buffer.

 class FillAndEmpty {
 Rendezvous exchanger = new Rendezvous(2);
 Buffer initialEmptyBuffer = ... a made-up type
 Buffer initialFullBuffer = ...
 class FillingLoop implements Runnable {
 public void run() {
 Buffer currentBuffer = initialEmptyBuffer;
 try {
 while (currentBuffer != null) {
 addToBuffer(currentBuffer);
 if (currentBuffer.full()) 
 currentBuffer = (Buffer)(exchanger.rendezvous(currentBuffer));
 }
 }
 catch (BrokenBarrierException ex) {
 return;
 }
 catch (InterruptedException ex) {
 Thread.currentThread().interrupt();
 }
 }
 }
 class EmptyingLoop implements Runnable {
 public void run() {
 Buffer currentBuffer = initialFullBuffer;
 try {
 while (currentBuffer != null) {
 takeFromBuffer(currentBuffer);
 if (currentBuffer.empty()) 
 currentBuffer = (Buffer)(exchanger.rendezvous(currentBuffer));
 }
 }
 catch (BrokenBarrierException ex) {
 return;
 }
 catch (InterruptedException ex) {
 Thread.currentThread().interrupt();
 }
 }
 }
 void start() {
 new Thread(new FillingLoop()).start();
 new Thread(new EmptyingLoop()).start();
 }
 }
 

[ Introduction to this package. ]