org.metasyntactic.thread.concurrent
Class Latch

java.lang.Object
  |
  +--org.metasyntactic.thread.concurrent.Latch

All Implemented Interfaces:

Monitor

public class Latch

extends java.lang.Object

implements Monitor

A latch is a boolean condition that is set at most once, ever. Once a single release is issued, all acquires will pass.

Sample usage. Here are a set of classes that use a latch as a start signal for a group of worker threads that are created and started beforehand, and then later enabled.

  class Worker implements Runnable {
    private final Latch startSignal;
    Worker(Latch l) { startSignal = l; }
     public void run() {
       startSignal.acquire();
       doWork();
    }
    void doWork() { ... }
  }

  class Driver { // ...
    void main() {
      Latch go = new Latch();
      for (int i = 0; i < N; ++i) // make threads
        new Thread(new Worker(go)).start();
      doSomethingElse();         // don't let run yet
      go.release();              // let all threads proceed
    }
  }
 

Field Summary

Fields inherited from interface org.metasyntactic.thread.concurrent.Monitor

ONE_CENTURY, ONE_DAY, ONE_HOUR, ONE_MINUTE, ONE_SECOND, ONE_WEEK, ONE_YEAR

Constructor Summary

Latch()

Method Summary

void	acquire() Wait (possibly forever) until successful passage.
boolean	attempt(long msecs) Wait at most msecs to pass; report whether passed.
void	release() Enable all current and future acquires to pass

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Latch

public Latch()

Method Detail

acquire

public void acquire()
             throws java.lang.InterruptedException

Description copied from interface: Monitor

Wait (possibly forever) until successful passage. Fail only upon interuption. Interruptions always result in `clean' failures. On failure, you can be sure that it has not been acquired, and that no corresponding release should be performed. Conversely, a normal return guarantees that the acquire was successful.

Specified by:

acquire in interface Monitor

java.lang.InterruptedException

attempt

public boolean attempt(long msecs)
                throws java.lang.InterruptedException

Description copied from interface: Monitor

Wait at most msecs to pass; report whether passed.

The method has best-effort semantics: The msecs bound cannot be guaranteed to be a precise upper bound on wait time in Java. Implementations generally can only attempt to return as soon as possible after the specified bound. Also, timers in Java do not stop during garbage collection, so timeouts can occur just because a GC intervened. So, msecs arguments should be used in a coarse-grained manner. Further, implementations cannot always guarantee that this method will return at all without blocking indefinitely when used in unintended ways. For example, deadlocks may be encountered when called in an unintended context.

Specified by:

attempt in interface Monitor

Parameters:

msecs -

Returns:

Throws:

java.lang.InterruptedException

release

public void release()

Enable all current and future acquires to pass

Specified by:

release in interface Monitor