Scala example source code file (SynchronizedPriorityQueue.scala)

This example Scala source code file (SynchronizedPriorityQueue.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Scala source code examples by using tags.

All credit for the original source code belongs to scala-lang.org; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Scala tags/keywords

a, boolean, comprehensive, consider, iterator, ordering, priorityqueue, string, traversableonce, unit

The SynchronizedPriorityQueue.scala Scala example source code

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2003-2013, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |                                         **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */



package scala
package collection
package mutable

/** This class implements synchronized priority queues using a binary heap.
 *  The elements of the queue have to be ordered in terms of the `Ordered[T]` class.
 *
 *  @tparam A    type of the elements contained in this synchronized priority queue
 *  @param ord   implicit ordering used to compared elements of type `A`
 *
 *  @author  Matthias Zenger
 *  @version 1.0, 03/05/2004
 *  @since   1
 *  @define Coll `SynchronizedPriorityQueue`
 *  @define coll synchronized priority queue
 */
@deprecated("Comprehensive synchronization via selective overriding of methods is inherently unreliable.  Consider java.util.concurrent.ConcurrentSkipListSet as an alternative.", "2.11.0")
class SynchronizedPriorityQueue[A](implicit ord: Ordering[A]) extends PriorityQueue[A] {

  /** Checks if the queue is empty.
   *
   *  @return true, iff there is no element in the queue.
   */
  override def isEmpty: Boolean = synchronized { super.isEmpty }

  /** Inserts a single element into the priority queue.
   *
   *  @param  elem        the element to insert
   */
  override def +=(elem: A): this.type = {
    synchronized {
      super.+=(elem)
    }
    this
  }

  /** Adds all elements of a traversable object into the priority queue.
   *
   *  @param  xs        a traversable object
   */
  override def ++=(xs: TraversableOnce[A]): this.type = {
    synchronized {
      super.++=(xs)
    }
    this
  }

  /** Adds all elements to the queue.
   *
   *  @param  elems       the elements to add.
   */
  override def enqueue(elems: A*): Unit = synchronized { super.++=(elems) }

  /** Returns the element with the highest priority in the queue,
   *  and removes this element from the queue.
   *
   *  @return   the element with the highest priority.
   */
  override def dequeue(): A = synchronized { super.dequeue() }

  /** Returns the element with the highest priority in the queue,
   *  or throws an error if there is no element contained in the queue.
   *
   *  @return   the element with the highest priority.
   */
  override def head: A = synchronized { super.head }

  /** Removes all elements from the queue. After this operation is completed,
   *  the queue will be empty.
   */
  override def clear(): Unit = synchronized { super.clear() }

  /** Returns an iterator which yield all the elements of the priority
   *  queue in descending priority order.
   *
   *  @return  an iterator over all elements sorted in descending order.
   */
  override def iterator: Iterator[A] = synchronized { super.iterator }

  /** Checks if two queues are structurally identical.
   *
   *  @return true, iff both queues contain the same sequence of elements.
   */
  override def equals(that: Any): Boolean = synchronized { super.equals(that) }

  /** Returns a textual representation of a queue as a string.
   *
   *  @return the string representation of this queue.
   */
  override def toString(): String = synchronized { super.toString() }
}