Class LayeredSync

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

public class LayeredSync extends Object implements Sync
A class that can be used to compose Syncs. A LayeredSync object manages two other Sync objects, outer and inner. The acquire operation invokes outer.acquire() followed by inner.acquire(), but backing out of outer (via release) upon an exception in inner. The other methods work similarly.

LayeredSyncs can be used to compose arbitrary chains by arranging that either of the managed Syncs be another LayeredSync.

[ Introduction to this package. ]

  • Field Details

    • outer_

      protected final Sync outer_
    • inner_

      protected final Sync inner_
  • Constructor Details

    • LayeredSync

      public LayeredSync(Sync outer, Sync inner)
      Create a LayeredSync managing the given outer and inner Sync objects
  • 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()
      Description copied from interface: Sync
      Potentially enable others to pass.

      Because release does not raise exceptions, it can be used in `finally' clauses without requiring extra embedded try/catch blocks. But keep in mind that as with any java method, implementations may still throw unchecked exceptions such as Error or NullPointerException when faced with uncontinuable errors. However, these should normally only be caught by higher-level error handlers.

      Specified by:
      release in interface Sync