All Known Subinterfaces:

BytePriorityQueue, CharPriorityQueue, DoublePriorityQueue, FloatPriorityQueue, IntPriorityQueue, LongPriorityQueue, ShortPriorityQueue

All Known Implementing Classes:

AbstractBytePriorityQueue, AbstractCharPriorityQueue, AbstractDoublePriorityQueue, AbstractFloatPriorityQueue, AbstractIntPriorityQueue, AbstractLongPriorityQueue, AbstractPriorityQueue, AbstractShortPriorityQueue, ByteArrayFIFOQueue, ByteArrayPriorityQueue, ByteHeapPriorityQueue, BytePriorityQueues.SynchronizedPriorityQueue, CharArrayFIFOQueue, CharArrayPriorityQueue, CharHeapPriorityQueue, CharPriorityQueues.SynchronizedPriorityQueue, DoubleArrayFIFOQueue, DoubleArrayPriorityQueue, DoubleHeapPriorityQueue, DoublePriorityQueues.SynchronizedPriorityQueue, FloatArrayFIFOQueue, FloatArrayPriorityQueue, FloatHeapPriorityQueue, FloatPriorityQueues.SynchronizedPriorityQueue, IntArrayFIFOQueue, IntArrayPriorityQueue, IntHeapPriorityQueue, IntPriorityQueues.SynchronizedPriorityQueue, LongArrayFIFOQueue, LongArrayPriorityQueue, LongHeapPriorityQueue, LongPriorityQueues.SynchronizedPriorityQueue, ObjectArrayFIFOQueue, ObjectArrayPriorityQueue, ObjectHeapPriorityQueue, PriorityQueues.EmptyPriorityQueue, PriorityQueues.SynchronizedPriorityQueue, ShortArrayFIFOQueue, ShortArrayPriorityQueue, ShortHeapPriorityQueue, ShortPriorityQueues.SynchronizedPriorityQueue
```
public interface PriorityQueue<K>
```
A priority queue.
A priority queue provides a way to enqueue elements, and to dequeue them in some specified order. Elements that are smaller in the specified order are dequeued first. It is also possible to get the first element, that is, the element that would be dequeued next.
Additionally, the queue may provide a method to peek at element that would be dequeued last.
The relative order of the elements enqueued should not change during queue operations. Nonetheless, some implementations may give the caller a way to notify the queue that the first element has changed its relative position in the order.

Method Summary

Modifier and Type	Method	Description
`default void`	`changed()`	Notifies the queue that the first element has changed (optional operation).
`void`	`clear()`	Removes all elements from this queue.
`Comparator<? super K>`	`comparator()`	Returns the comparator associated with this queue, or `null` if it uses its elements' natural ordering.
`K`	`dequeue()`	Dequeues the first element from the queue.
`void`	`enqueue(K x)`	Enqueues a new element.
`K`	`first()`	Returns the first element of the queue.
`default boolean`	`isEmpty()`	Checks whether this queue is empty.
`default K`	`last()`	Returns the last element of the queue, that is, the element the would be dequeued last (optional operation).
`int`	`size()`	Returns the number of elements in this queue.

- Method Detail
  - enqueue
```
void enqueue(K x)
```
    Enqueues a new element.
    
    Parameters:
    
    x - the element to enqueue.
  - dequeue
```
K dequeue()
```
    Dequeues the first element from the queue.
    
    Returns:
    
    the dequeued element.
    
    Throws:
    
    NoSuchElementException - if the queue is empty.
  - isEmpty
```
default boolean isEmpty()
```
    Checks whether this queue is empty.
    This default implementation checks whether size() is zero.
    
    Returns:
    
    true if this queue is empty.
  - size
```
int size()
```
    Returns the number of elements in this queue.
    
    Returns:
    
    the number of elements in this queue.
  - clear
```
void clear()
```
    Removes all elements from this queue.
  - first
```
K first()
```
    Returns the first element of the queue.
    
    Returns:
    
    the first element.
    
    Throws:
    
    NoSuchElementException - if the queue is empty.
  - last
```
default K last()
```
    Returns the last element of the queue, that is, the element the would be dequeued last (optional operation).
    This default implementation just throws an UnsupportedOperationException.
    
    Returns:
    
    the last element.
    
    Throws:
    
    NoSuchElementException - if the queue is empty.
  - changed
```
default void changed()
```
    Notifies the queue that the first element has changed (optional operation).
    This default implementation just throws an UnsupportedOperationException.
  - comparator
```
Comparator<? super K> comparator()
```
    Returns the comparator associated with this queue, or null if it uses its elements' natural ordering.
    
    Returns:
    
    the comparator associated with this sorted set, or null if it uses its elements' natural ordering.

Interface PriorityQueue<K>

Method Summary

Method Detail

enqueue

dequeue

isEmpty

size

clear

first

last

changed

comparator