EDU.oswego.cs.dl.util.concurrent

Class BoundedPriorityQueue

Implemented Interfaces:
BoundedChannel, Channel, Puttable, Takable

public class BoundedPriorityQueue
extends SemaphoreControlledChannel

A heap-based priority queue, using semaphores for concurrency control. The take operation returns the least element with respect to the given ordering. (If more than one element is tied for least value, one of them is arbitrarily chosen to be returned -- no guarantees are made for ordering across ties.) Ordering follows the JDK1.2 collection conventions: Either the elements must be Comparable, or a Comparator must be supplied. Comparison failures throw ClassCastExceptions during insertions and extractions. The implementation uses a standard array-based heap algorithm, as described in just about any data structures textbook.

Put and take operations may throw ClassCastException if elements are not Comparable, or not comparable using the supplied comparator. Since not all elements are compared on each operation it is possible that an exception will not be thrown during insertion of non-comparable element, but will later be encountered during another insertion or extraction.

[ Introduction to this package. ]

Field Summary

protected Heap
heap_

Fields inherited from class EDU.oswego.cs.dl.util.concurrent.SemaphoreControlledChannel

capacity_, putGuard_, takeGuard_

Constructor Summary

BoundedPriorityQueue()
Create a priority queue with the current default capacity and relying on natural ordering.
BoundedPriorityQueue(Comparator comparator)
Create a priority queue with the current default capacity and the given comparator
BoundedPriorityQueue(int capacity)
Create a priority queue with the given capacity, and relying on natural ordering.
BoundedPriorityQueue(int capacity, Comparator cmp)
Create a priority queue with the given capacity and comparator
BoundedPriorityQueue(int capacity, Comparator cmp, Class semaphoreClass)
Create a priority queue with the given capacity and comparator, using the supplied Semaphore class for semaphores.

Method Summary

protected Object
extract()
protected void
insert(Object x)
Object
peek()
Return, but do not remove object at head of Channel, or null if it is empty.

Methods inherited from class EDU.oswego.cs.dl.util.concurrent.SemaphoreControlledChannel

capacity, extract, insert, offer, poll, put, size, take

Field Details

heap_

protected final Heap heap_

Constructor Details

BoundedPriorityQueue

public BoundedPriorityQueue()
Create a priority queue with the current default capacity and relying on natural ordering.

BoundedPriorityQueue

public BoundedPriorityQueue(Comparator comparator)
Create a priority queue with the current default capacity and the given comparator

BoundedPriorityQueue

public BoundedPriorityQueue(int capacity)
Create a priority queue with the given capacity, and relying on natural ordering.

BoundedPriorityQueue

public BoundedPriorityQueue(int capacity,
                            Comparator cmp)
            throws IllegalArgumentException
Create a priority queue with the given capacity and comparator

BoundedPriorityQueue

public BoundedPriorityQueue(int capacity,
                            Comparator cmp,
                            Class semaphoreClass)
            throws IllegalArgumentException,
                   NoSuchMethodException,
                   SecurityException,
                   InstantiationException,
                   IllegalAccessException,
                   InvocationTargetException
Create a priority queue with the given capacity and comparator, using the supplied Semaphore class for semaphores.

Method Details

extract

protected Object extract()
Overrides:
extract in interface SemaphoreControlledChannel

insert

protected void insert(Object x)
Overrides:
insert in interface SemaphoreControlledChannel

peek

public Object peek()
Return, but do not remove object at head of Channel, or null if it is empty.
Specified by:
peek in interface Channel