org.metasyntactic.thread.concurrent
Class FirstInFirstOutSemaphore

java.lang.Object
  |
  +--org.metasyntactic.thread.concurrent.Semaphore
        |
        +--org.metasyntactic.thread.concurrent.QueuedSemaphore
              |
              +--org.metasyntactic.thread.concurrent.FirstInFirstOutSemaphore
All Implemented Interfaces:
Monitor

public class FirstInFirstOutSemaphore
extends QueuedSemaphore

A First-in/First-out implementation of a Semaphore. Waiting requests will be satisified in the order that the processing of those requests got to a certain point. If this sounds vague it is meant to be. FIFO implies a logical timestamping at some point in the processing of the request. To simplify things we don't actually timestamp but simply store things in a FIFO queue. Thus the order in which requests enter the queue will be the order in which they come out. This order need not have any relationship to the order in which requests were made, nor the order in which requests actually return to the caller. These depend on Java thread scheduling which is not guaranteed to be predictable (although JVMs tend not to go out of their way to be unfair).


Nested Class Summary
protected static class FirstInFirstOutSemaphore.FirstInFirstOutWaitQueue
          Simple linked list queue used in FirstInFirstOutSemaphore.
 
Nested classes inherited from class org.metasyntactic.thread.concurrent.QueuedSemaphore
 
Field Summary
 
Fields inherited from class org.metasyntactic.thread.concurrent.Semaphore
permits
 
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
FirstInFirstOutSemaphore(long initialPermits)
          Create a Semaphore with the given initial number of permits.
 
Methods inherited from class org.metasyntactic.thread.concurrent.QueuedSemaphore
acquire, attempt, release, release
 
Methods inherited from class org.metasyntactic.thread.concurrent.Semaphore
permits
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

FirstInFirstOutSemaphore

public FirstInFirstOutSemaphore(long initialPermits)
Create a Semaphore with the given initial number of permits. Using a seed of one makes the semaphore act as a mutual exclusion lock. Negative seeds are also allowed, in which case no acquires will proceed until the number of releases has pushed the number of permits past 0.

Parameters:
initialPermits -