Package com.groiss.ds

Class CountedSemaphore

java.lang.Object

java.util.concurrent.Semaphore

com.groiss.ds.CountedSemaphore

All Implemented Interfaces:

Serializable

public class CountedSemaphore
extends Semaphore

A CountedSemaphore (from Dijkstra) where waiting threads are handled in FIFO order. Moreover you can specify the amount of threads waiting for the resource. If the waiting queue is full the next caller will receive an QueueFullException.

See Also:

• Serialized Form

Constructor Summary

Constructors

Constructor	Description
CountedSemaphore(int threadsRunning)	Construct a new semaphore.
CountedSemaphore(int threadsRunning, int threadsWaiting)	Construct a new semaphore.

Method Summary

Modifier and Type	Method	Description
static void	addSemaphore(String id, CountedSemaphore s)	Add a new semaphore to the semaphore table
static CountedSemaphore	getSemaphore(String id)	Get the semaphore with key 'id' from the semaphore table
void	P()	Enter the critical section.
void	V()	Leave the critical section.

Methods inherited from class java.util.concurrent.Semaphore

acquire, acquire, acquireUninterruptibly, acquireUninterruptibly, availablePermits, drainPermits, getQueuedThreads, getQueueLength, hasQueuedThreads, isFair, reducePermits, release, release, toString, tryAcquire, tryAcquire, tryAcquire, tryAcquire

Methods inherited from class java.lang.Object

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

Constructor Details

CountedSemaphore

public CountedSemaphore(int threadsRunning)

Construct a new semaphore.

Parameters:

threadsRunning - how many threads can go into the critical section.

CountedSemaphore

public CountedSemaphore(int threadsRunning,
 int threadsWaiting)

Construct a new semaphore.

Parameters:

threadsRunning - how many threads can go into the critical section.

threadsWaiting - how many threads may wait.

Method Details

getSemaphore

public static CountedSemaphore getSemaphore(String id)

Get the semaphore with key 'id' from the semaphore table

addSemaphore

public static void addSemaphore(String id,
 CountedSemaphore s)

Add a new semaphore to the semaphore table

P

public void P()
       throws QueueFullException,
InterruptedException

Enter the critical section.

Throws:

QueueFullException - when waiting queue is full.

InterruptedException

V

public void V()

Leave the critical section.