Class Latch

java.lang.Object
EDU.oswego.cs.dl.util.concurrent.Latch
All Implemented Interfaces:
Sync

public class Latch extends Object implements Sync
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 invalid input: '<' N; ++i) // make threads
       new Thread(new Worker(go)).start();
     doSomethingElse();         // don't let run yet 
     go.release();              // let all threads proceed
   } 
 }
[ Introduction to this package. ]

  • Field Details

    • latched_

      protected boolean latched_
  • Constructor Details

    • Latch

      public Latch()
  • Method Details

    • acquire

      public void acquire() throws InterruptedException
      Description copied from interface: Sync
      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 Sync
      Throws:
      InterruptedException
    • attempt

      public boolean attempt(long msecs) throws InterruptedException
      Description copied from interface: Sync
      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 Sync
      Parameters:
      msecs - the number of milleseconds to wait. An argument less than or equal to zero means not to wait at all. However, this may still require access to a synchronization lock, which can impose unbounded delay if there is a lot of contention among threads.
      Returns:
      true if acquired
      Throws:
      InterruptedException
    • release

      public void release()
      Enable all current and future acquires to pass
      Specified by:
      release in interface Sync