E - the type of elements held in this queue
Serializable, Iterable<E>, Collection<E>, Queue<E>
An unbounded priority
queuebased 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 (doing so may result in
ClassCastException
).
The head of this queue is the least element with respect to the specified ordering. If multiple elements are tied for least value, the head is one of those elements -- ties are broken arbitrarily. The queue retrieval operations poll, remove, peek, and element access the element at the head of the queue.
A priority queue is unbounded, but has an internal capacity governing the size of an array used to store the elements on the queue. It is always at least as large as the queue size. As elements are added to a priority queue, its capacity grows automatically. The details of the growth policy are not specified.
This class and its iterator implement all of the optional methods of the Collection and Iterator interfaces. The Iterator provided in method iterator() and the Spliterator provided in method spliterator() are not guaranteed to traverse the elements of the priority queue in any particular order. If you need ordered traversal, consider using Arrays.sort(pq.toArray()).
Note that this implementation is not synchronized. Multiple threads should not access a PriorityQueue instance concurrently if any of the threads modifies the queue. Instead, use the thread-safe PriorityBlockingQueue class.
Implementation note: this implementation provides O(log(n)) time for the enqueuing and dequeuing methods (offer, poll, remove() and add); linear time for the remove(Object) and contains(Object) methods; and constant time for the retrieval methods (peek, element, and size).
This class is a member of the Java Collections Framework.
Constructors
Creates a
PriorityQueue
with the default initial capacity (11) that orders its elements according to their
natural ordering.
Creates a
PriorityQueue
with the specified initial capacity that orders its elements according to their
natural ordering.
Creates a PriorityQueue with the specified initial capacity that orders its elements according to the specified comparator.
Creates a PriorityQueue containing the elements in the specified collection.
Creates a PriorityQueue with the default initial capacity and whose elements are ordered according to the specified comparator.
Creates a PriorityQueue containing the elements in the specified priority queue.
Creates a PriorityQueue containing the elements in the specified sorted set.
boolean
Inserts the specified element into this priority queue.
void
Removes all of the elements from this priority queue.
Returns the comparator used to order the elements in this queue, or
null
if this queue is sorted according to the
natural orderingof its elements.
boolean
Returns true if this queue contains the specified element.
void
Performs the given action for each element of the Iterable until all elements have been processed or the action throws an exception.
Returns an iterator over the elements in this queue.
boolean
Inserts the specified element into this priority queue.
Retrieves, but does not remove, the head of this queue, or returns null if this queue is empty.
Retrieves and removes the head of this queue, or returns null if this queue is empty.
boolean
Removes a single instance of the specified element from this queue, if it is present.
boolean
Removes all of this collection's elements that are also contained in the specified collection (optional operation).
boolean
Removes all of the elements of this collection that satisfy the given predicate.
boolean
Retains only the elements in this collection that are contained in the specified collection (optional operation).
int
Returns the number of elements in this collection.
Returns an array containing all of the elements in this queue.
<T> T[]
Returns an array containing all of the elements in this queue; the runtime type of the returned array is that of the specified array.
public PriorityQueue()
Creates a
PriorityQueue
with the default initial capacity (11) that orders its elements according to their
natural ordering.
public PriorityQueue(int initialCapacity)
Creates a
PriorityQueue
with the specified initial capacity that orders its elements according to their
natural ordering.
initialCapacity - the initial capacity for this priority queue
IllegalArgumentException - if initialCapacity is less than 1
Creates a PriorityQueue with the default initial capacity and whose elements are ordered according to the specified comparator.
comparator - the comparator that will be used to order this priority queue. If null, the natural ordering of the elements will be used.
Creates a PriorityQueue with the specified initial capacity that orders its elements according to the specified comparator.
initialCapacity - the initial capacity for this priority queue
comparator - the comparator that will be used to order this priority queue. If null, the natural ordering of the elements will be used.
IllegalArgumentException - if initialCapacity is less than 1
Creates a
PriorityQueue
containing the elements in the specified collection. If the specified collection is an instance of a
SortedSet
or is another
PriorityQueue
, this priority queue will be ordered according to the same ordering. Otherwise, this priority queue will be ordered according to the
natural orderingof its elements.
c - the collection whose elements are to be placed into this priority queue
ClassCastException - if elements of the specified collection cannot be compared to one another according to the priority queue's ordering
NullPointerException - if the specified collection or any of its elements are null
Creates a PriorityQueue containing the elements in the specified priority queue. This priority queue will be ordered according to the same ordering as the given priority queue.
c - the priority queue whose elements are to be placed into this priority queue
ClassCastException - if elements of c cannot be compared to one another according to c's ordering
NullPointerException - if the specified priority queue or any of its elements are null
Creates a PriorityQueue containing the elements in the specified sorted set. This priority queue will be ordered according to the same ordering as the given sorted set.
c - the sorted set whose elements are to be placed into this priority queue
ClassCastException - if elements of the specified sorted set cannot be compared to one another according to the sorted set's ordering
NullPointerException - if the specified sorted set or any of its elements are null
Inserts the specified element into this priority queue.
add in interface Collection<E>
add in interface Queue<E>
add in class AbstractQueue<E>
e - the element to add
true (as specified by Collection.add(E))
ClassCastException - if the specified element cannot be compared with elements currently in this priority queue according to the priority queue's ordering
NullPointerException - if the specified element is null
Inserts the specified element into this priority queue.
offer in interface Queue<E>
e - the element to add
true (as specified by Queue.offer(E))
ClassCastException - if the specified element cannot be compared with elements currently in this priority queue according to the priority queue's ordering
NullPointerException - if the specified element is null
Queue
Retrieves, but does not remove, the head of this queue, or returns null if this queue is empty.
Removes a single instance of the specified element from this queue, if it is present. More formally, removes an element e such that o.equals(e), if this queue contains one or more such elements. Returns true if and only if this queue contained the specified element (or equivalently, if this queue changed as a result of the call).
remove in interface Collection<E>
remove in class AbstractCollection<E>
o - element to be removed from this queue, if present
true if this queue changed as a result of the call
Returns true if this queue contains the specified element. More formally, returns true if and only if this queue contains at least one element e such that o.equals(e).
contains in interface Collection<E>
contains in class AbstractCollection<E>
o - object to be checked for containment in this queue
true if this queue contains the specified element
Returns an array containing all of the elements in this queue. The elements are in no particular order.
The returned array will be "safe" in that no references to it are maintained by this queue. (In other words, this method must allocate a new array). The caller is thus free to modify the returned array.
This method acts as bridge between array-based and collection-based APIs.
toArray in interface Collection<E>
toArray in class AbstractCollection<E>
public <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. The returned array elements are in no particular order. If the queue fits in the specified array, it is returned therein. Otherwise, a new array is allocated with the runtime type of the specified array and the size of this queue.
If the queue fits in the specified array with room to spare (i.e., the array has more elements than the queue), the element in the array immediately following the end of the collection is set to null.
Like the toArray() method, this method acts as bridge between array-based and collection-based APIs. Further, this method allows precise control over the runtime type of the output array, and may, under certain circumstances, be used to save allocation costs.
Suppose x is a queue known to contain only strings. The following code can be used to dump the queue into a newly allocated array of String:
String[] y = x.toArray(new String[0]);
Note that
toArray(new Object[0])
is identical in function to
toArray()
.
toArray in interface Collection<E>
toArray in class AbstractCollection<E>
T - the component type of the array to contain the collection
a - the array into which the elements of the queue are to be stored, if it is big enough; otherwise, a new array of the same runtime type is allocated for this purpose.
ArrayStoreException - if the runtime type of the specified array is not a supertype of the runtime type of every element in this queue
NullPointerException - if the specified array is null
Returns an iterator over the elements in this queue. The iterator does not return the elements in any particular order.
iterator in interface Collection<E>
iterator in interface Iterable<E>
iterator in class AbstractCollection<E>
public int size()
Returns the number of elements in this collection. If this collection contains more than Integer.MAX_VALUE elements, returns Integer.MAX_VALUE.
size in interface Collection<E>
public void clear()
Removes all of the elements from this priority queue. The queue will be empty after this call returns.
clear in interface Collection<E>
clear in class AbstractQueue<E>
Queue
Retrieves and removes the head of this queue, or returns null if this queue is empty.
Returns the comparator used to order the elements in this queue, or
null
if this queue is sorted according to the
natural orderingof its elements.
null if this queue is sorted according to the natural ordering of its elements
spliterator in interface Collection<E>
spliterator in interface Iterable<E>
Spliterator over the elements in this queue
Removes all of the elements of this collection that satisfy the given predicate. Errors or runtime exceptions thrown during iteration or by the predicate are relayed to the caller.
removeIf in interface Collection<E>
filter - a predicate which returns true for elements to be removed
true if any elements were removed
NullPointerException - if the specified filter is null
Removes all of this collection's elements that are also contained in the specified collection (optional operation). After this call returns, this collection will contain no elements in common with the specified collection.
removeAll in interface Collection<E>
removeAll in class AbstractCollection<E>
c - collection containing elements to be removed from this collection
true if this collection changed as a result of the call
NullPointerException - if this collection contains one or more null elements and the specified collection does not support null elements (optional), or if the specified collection is null
Retains only the elements in this collection that are contained in the specified collection (optional operation). In other words, removes from this collection all of its elements that are not contained in the specified collection.
retainAll in interface Collection<E>
retainAll in class AbstractCollection<E>
c - collection containing elements to be retained in this collection
true if this collection changed as a result of the call
NullPointerException - if this collection contains one or more null elements and the specified collection does not permit null elements (optional), or if the specified collection is null
Iterable
Performs the given action for each element of the
Iterable
until all elements have been processed or the action throws an exception. Actions are performed in the order of iteration, if that order is specified. Exceptions thrown by the action are relayed to the caller.
The behavior of this method is unspecified if the action performs side-effects that modify the underlying source of elements, unless an overriding class has specified a concurrent modification policy.
forEach in interface Iterable<E>
action - The action to be performed for each element
NullPointerException - if the specified action is null
RetroSearch is an open source project built by @garambo | Open a GitHub Issue
Search and Browse the WWW like it's 1997 | Search results from DuckDuckGo
HTML:
3.2
| Encoding:
UTF-8
| Version:
0.7.4