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