What is the PriorityQueue class?
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The PriorityQueue class extends the AbstractQueue class and implements the Queue interface. The Queue interface normally stores elements in the first-in-first-out order. A PriorityQueue stores elements either in the natural order or in the order specified by a comparator.
The important constructors defined in the PriorityQueue class are as follows:
- PriorityQueue(): This constructor builds an empty queue with an initial capacity of 11.
- PriorityQueue(int capacity): This constructor builds a PriorityQueue with the specified initial capacity.
- PriorityQueue(int capcity, Comparator< ? super E > comp): This constructor builds a PriorityQueue with the specified initial capacity and a comparator.
- PriorityQueue(Collection < ? extends E > c): This constructor builds a PriorityQueue that is initialized with the elements of the collection c.
The important methods defined in the PriorityQueue class are as follows:
- E element(): This method returns the element at the head of the queue. It does not remove the element from the queue. It throws a NoSuchElementException if the queue is empty.
- E peek(): This method also returns the element at the head of the queue without removing it from the queue. However, it returns a null if the queue is empty.
- E remove(): This method returns the element at the head of the queue. It also removes the element from the queue. It throws a NoSuchElementException if the queue is empty.
- E poll: This method returns the element at the head of the queue. It also removes the element from the queue. However, it returns a null if the queue is empty.
- Boolean offer(E obj): This method tries to add obj to the queue. It returns true if the object was added and false otherwise.
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