![]() Implementation note: this implementation provides Instead, use the thread-safe PriorityBlockingQueue class. Instance concurrently if any of the threads modifies the queue. Multiple threads should not access a PriorityQueue Note that this implementation is not synchronized. Traversal, consider using Arrays.sort(pq.toArray()). The priority queue in any particular order. The Iterator provided in method iterator() and the Spliterator provided in method spliterator()Īre not guaranteed to traverse the elements of Optional methods of the Collection and Iterator interfaces. This class and its iterator implement all of the As elements are added to a priority queue, its capacity It is always at least as large as the queue The queue retrieval operations poll,Ī priority queue is unbounded, but has an internalĬapacity governing the size of an array used to store theĮlements on the queue. Tied for least value, the head is one of those elements - ties areīroken arbitrarily. The head of this queue is the least element Insertion of non-comparable objects (doing so may result in A priority queue does not permit null elements.Ī priority queue relying on natural ordering also does not permit Provided at queue construction time, depending on which constructor is The elements of the priority queue are ordered according to their Therefore, it would be wrong to write a program that depended on thisĮxception for its correctness: the fail-fast behavior of iterators should be used only toĭetect bugs.An unbounded priority queue based on a priority heap. Fail-fast iterators throw ConcurrentModificationException on aīest-effort basis. Speaking, impossible to make any hard guarantees in the presence of unsynchronized concurrent Note that the fail-fast behavior of an iterator cannot be guaranteed as it is, generally Non-deterministic behavior at an undetermined time in the future. Thus, in the face ofĬoncurrent modification, the iterator fails quickly and cleanly, rather than risking arbitrary, Iterator will generally throw a ConcurrentModificationException. The iterator is created, in any way except through the iterator's own remove method, the The iterator is fail-fast: If the MinMaxPriorityQueue is modified at any time after Returns an iterator over the elements contained in this collection, in no particular Since: 8.0 Author: Sverre Sundsdal, Torbjorn Gannholm If you only access one end of the queue, and don't use a maximum size, this class isįunctionally equivalent to PriorityQueue, but significantly slower.The AbstractCollection.remove(Object) and ntains() operations require linear ( O(n)).Poll() and AbstractQueue.remove()) run in O(log n) time. The enqueuing and dequeuing operations ( offer(E), add(E), and all the forms of.The retrieval operations peek(), peekFirst(), peekLast(), AbstractQueue.element(), and size are constant-time. ![]() ![]() Improved (and asymptotically superior) performance. In many cases Ordering.leastOf(, int) may work for your use case with significantly Significantly worse than a PriorityQueue with manual eviction above the maximum If you only access one end of the queue, and do use a maximum size, this class will perform.This class is not thread-safe, and does not accept null elements. Unlike many other double-ended priority queues, it stores elements in a single array, as compactĪs the traditional heap data structure used in PriorityQueue. This implementation is based on the min-max heap developed by Atkinson, et al. This is different fromĬonventional bounded queues, which either block or reject new elements when full. Its comparator (which might be the element that was just added). The queue exceeds that value, the queue automatically removes its greatest element according to But unlikeĪ regular priority queue, the methods peekLast(), pollLast() and removeLast() are also provided, to act on the greatest element in the queue instead.Ī min-max priority queue can be configured with a maximum size. Implicit target of the methods peek(), poll() and AbstractQueue.remove() - isĭefined as the least element in the queue according to the queue's comparator. MinMaxPriorityQueue users = MinMaxPriorityQueue.orderedBy(userComparator)Īs a Queue it functions exactly as a PriorityQueue: its head element - the Given at creation time, the natural order of elements is used. Its greatest element, as determined by the queue's specified comparator. A double-ended priority queue, which provides constant-time access to both its least element and
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