Java.util.PriorityQueue Class
Java PriorityQueue Class
Java.util package provides a PriorityQueue class where an unbounded priority queue based on a priority heap. The elements of the priority queue are ordered according to their natural ordering, or by a Comparator provided at queue construction time, depending on which constructor is used. A priority queue does not permit null elements. A priority queue relying on natural ordering also does not permit insertion of non-comparable objects.
Class declaration
The declaration of java.util.PriorityQueue class is:
public class PriorityQueue<E>
extends AbstractQueue<E>
implements Serializable
Here, E is the type of element maintained by the container.
Class Constructors
| S.N | Constructors & Description |
|---|---|
| 1. |
PriorityQueue() Creates a PriorityQueue with the default initial capacity (11) that orders its elements according to their natural ordering. |
| 2. |
PriorityQueue(Collection<? extends E> c) Creates a PriorityQueue containing the elements in the specified collection. |
| 3. |
PriorityQueue(Comparator<? super E> comparator) Creates a PriorityQueue with the default initial capacity and whose elements are ordered according to the specified comparator. |
| 4. |
PriorityQueue(int initialCapacity) Creates a PriorityQueue with the specified initial capacity that orders its elements according to their natural ordering. |
| 5. |
PriorityQueue(int initialCapacity, Comparator<? super E> comparator) Creates a PriorityQueue with the specified initial capacity that orders its elements according to the specified comparator. |
| 6. |
PriorityQueue(PriorityQueue<? extends E> c) Creates a PriorityQueue containing the elements in the specified priority queue. |
| 7. |
PriorityQueue(SortedSet<? extends E> c) Creates a PriorityQueue containing the elements in the specified sorted set. |
java.util.PriorityQueue Methods
The java.util.PriorityQueue class has a number of methods which are listed below:
Member Methods
| S.N | Methods & Description |
|---|---|
| 1. |
boolean add(E element) Inserts the specified element into this priority queue. |
| 2. |
void clear() Removes all of the elements from this priority queue. |
| 3. |
Comparator<? super E> comparator() Returns the comparator used to order the elements in this queue, or null if this queue is sorted according to the natural ordering of its elements. |
| 4. |
boolean contains(Object obj) Returns true if the queue contains the specified element. |
| 5. |
Iterator<E> iterator() Returns an iterator over the elements in this queue. |
| 6. |
boolean offer(E element) Inserts the specified element into this priority queue. |
| 7. |
E peek() Retrieves, but does not remove, the head of this queue, or returns null if this queue is empty. |
| 8. |
E poll() Retrieves and removes the head of this queue, or returns null if this queue is empty. |
| 9. |
boolean remove(Object obj) Removes a single instance of the specified element from this queue, if it is present. |
| 10. |
int size() Returns the number of elements in this queue. |
| 11. |
Spliterator<E> spliterator() Creates a late-binding and fail-fast spliterator over the elements in this queue. |
| 12. |
Object[] toArray() Returns an array containing all of the elements in this queue. |
| 13. |
<T> T[] toArray(T[] a) Returns an array containing all of the elements in this queue; the runtime type of the returned array is that of the specified array. |
Methods inherited
This class inherits the methods of following class:
- java.lang.Object
- java.util.AbstractCollection<E>
- java.util.AbstractQueue<E>
