EDU.oswego.cs.dl.util.concurrent
Class BoundedPriorityQueue

java.lang.Object
  EDU.oswego.cs.dl.util.concurrent.SemaphoreControlledChannel
      EDU.oswego.cs.dl.util.concurrent.BoundedPriorityQueue

All 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(java.util.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, java.util.Comparator cmp)
Create a priority queue with the given capacity and comparator

BoundedPriorityQueue(int capacity, java.util.Comparator cmp, java.lang.Class semaphoreClass)
Create a priority queue with the given capacity and comparator, using the supplied Semaphore class for semaphores.

Method Summary

protected java.lang.Object	extract() Internal mechanics of take.
protected void	insert(java.lang.Object x) Internal mechanics of put.
java.lang.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, offer, poll, put, size, take

Methods inherited from class java.lang.Object

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

Field Detail

heap_

protected final Heap heap_

Constructor Detail

BoundedPriorityQueue

public BoundedPriorityQueue(int capacity,
                            java.util.Comparator cmp)
                     throws java.lang.IllegalArgumentException

Create a priority queue with the given capacity and comparator

Throws:

java.lang.IllegalArgumentException - if capacity less or equal to zero

BoundedPriorityQueue

public BoundedPriorityQueue(java.util.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()

Create a priority queue with the current default capacity and relying on natural ordering.

BoundedPriorityQueue

public BoundedPriorityQueue(int capacity,
                            java.util.Comparator cmp,
                            java.lang.Class semaphoreClass)
                     throws java.lang.IllegalArgumentException,
                            java.lang.NoSuchMethodException,
                            java.lang.SecurityException,
                            java.lang.InstantiationException,
                            java.lang.IllegalAccessException,
                            java.lang.reflect.InvocationTargetException

Create a priority queue with the given capacity and comparator, using the supplied Semaphore class for semaphores.

Throws:

java.lang.IllegalArgumentException - if capacity less or equal to zero

java.lang.NoSuchMethodException - If class does not have constructor that intializes permits

java.lang.SecurityException - if constructor information not accessible

java.lang.InstantiationException - if semaphore class is abstract

java.lang.IllegalAccessException - if constructor cannot be called

java.lang.reflect.InvocationTargetException - if semaphore constructor throws an exception

Method Detail

insert

protected void insert(java.lang.Object x)

Description copied from class: SemaphoreControlledChannel

Internal mechanics of put.

Specified by:

insert in class SemaphoreControlledChannel

extract

protected java.lang.Object extract()

Description copied from class: SemaphoreControlledChannel

Internal mechanics of take.

Specified by:

extract in class SemaphoreControlledChannel

peek

public java.lang.Object peek()

Description copied from interface: Channel

Return, but do not remove object at head of Channel, or null if it is empty.