org.apache.commons.collections

Class BinaryHeap

public final class BinaryHeap extends AbstractCollection implements PriorityQueue, Buffer

Deprecated: Replaced by PriorityBuffer in buffer subpackage. Due to be removed in v4.0.

Binary heap implementation of PriorityQueue.

The PriorityQueue interface has now been replaced for most uses by the Buffer interface. This class and the interface are retained for backwards compatibility. The intended replacement is PriorityBuffer.

The removal order of a binary heap is based on either the natural sort order of its elements or a specified Comparator. The pop method always returns the first element as determined by the sort order. (The isMinHeap flag in the constructors can be used to reverse the sort order, in which case pop will always remove the last element.) The removal order is not the same as the order of iteration; elements are returned by the iterator in no particular order.

The insert and pop operations perform in logarithmic time. The peek operation performs in constant time. All other operations perform in linear time or worse.

Note that this implementation is not synchronized. Use SynchronizedPriorityQueue to provide synchronized access to a BinaryHeap:

 PriorityQueue heap = new SynchronizedPriorityQueue(new BinaryHeap());
 

Since: Commons Collections 1.0

Version: $Revision: 155406 $ $Date: 2005-02-26 12:55:26 +0000 (Sat, 26 Feb 2005) $

Author: Peter Donald Ram Chidambaram Michael A. Smith Paul Jack Stephen Colebourne

Constructor Summary
BinaryHeap()
Constructs a new minimum binary heap.
BinaryHeap(Comparator comparator)
Constructs a new BinaryHeap that will use the given comparator to order its elements.
BinaryHeap(int capacity)
Constructs a new minimum binary heap with the specified initial capacity.
BinaryHeap(int capacity, Comparator comparator)
Constructs a new BinaryHeap.
BinaryHeap(boolean isMinHeap)
Constructs a new minimum or maximum binary heap
BinaryHeap(boolean isMinHeap, Comparator comparator)
Constructs a new BinaryHeap.
BinaryHeap(int capacity, boolean isMinHeap)
Constructs a new minimum or maximum binary heap with the specified initial capacity.
BinaryHeap(int capacity, boolean isMinHeap, Comparator comparator)
Constructs a new BinaryHeap.
Method Summary
booleanadd(Object object)
Adds an object to this heap.
voidclear()
Clears all elements from queue.
Objectget()
Returns the priority element.
protected voidgrow()
Increases the size of the heap to support additional elements
voidinsert(Object element)
Inserts an element into queue.
booleanisEmpty()
Tests if queue is empty.
booleanisFull()
Tests if queue is full.
Iteratoriterator()
Returns an iterator over this heap's elements.
Objectpeek()
Returns the element on top of heap but don't remove it.
protected voidpercolateDownMaxHeap(int index)
Percolates element down heap from the position given by the index.
protected voidpercolateDownMinHeap(int index)
Percolates element down heap from the position given by the index.
protected voidpercolateUpMaxHeap(int index)
Percolates element up heap from from the position given by the index.
protected voidpercolateUpMaxHeap(Object element)
Percolates a new element up heap from the bottom.
protected voidpercolateUpMinHeap(int index)
Percolates element up heap from the position given by the index.
protected voidpercolateUpMinHeap(Object element)
Percolates a new element up heap from the bottom.
Objectpop()
Returns the element on top of heap and remove it.
Objectremove()
Removes the priority element.
intsize()
Returns the number of elements in this heap.
StringtoString()
Returns a string representation of this heap.

Constructor Detail

BinaryHeap

public BinaryHeap()
Constructs a new minimum binary heap.

BinaryHeap

public BinaryHeap(Comparator comparator)
Constructs a new BinaryHeap that will use the given comparator to order its elements.

Parameters: comparator the comparator used to order the elements, null means use natural order

BinaryHeap

public BinaryHeap(int capacity)
Constructs a new minimum binary heap with the specified initial capacity.

Parameters: capacity The initial capacity for the heap. This value must be greater than zero.

Throws: IllegalArgumentException if capacity is <= 0

BinaryHeap

public BinaryHeap(int capacity, Comparator comparator)
Constructs a new BinaryHeap.

Parameters: capacity the initial capacity for the heap comparator the comparator used to order the elements, null means use natural order

Throws: IllegalArgumentException if capacity is <= 0

BinaryHeap

public BinaryHeap(boolean isMinHeap)
Constructs a new minimum or maximum binary heap

Parameters: isMinHeap if true the heap is created as a minimum heap; otherwise, the heap is created as a maximum heap

BinaryHeap

public BinaryHeap(boolean isMinHeap, Comparator comparator)
Constructs a new BinaryHeap.

Parameters: isMinHeap true to use the order imposed by the given comparator; false to reverse that order comparator the comparator used to order the elements, null means use natural order

BinaryHeap

public BinaryHeap(int capacity, boolean isMinHeap)
Constructs a new minimum or maximum binary heap with the specified initial capacity.

Parameters: capacity the initial capacity for the heap. This value must be greater than zero. isMinHeap if true the heap is created as a minimum heap; otherwise, the heap is created as a maximum heap.

Throws: IllegalArgumentException if capacity is <= 0

BinaryHeap

public BinaryHeap(int capacity, boolean isMinHeap, Comparator comparator)
Constructs a new BinaryHeap.

Parameters: capacity the initial capacity for the heap isMinHeap true to use the order imposed by the given comparator; false to reverse that order comparator the comparator used to order the elements, null means use natural order

Throws: IllegalArgumentException if capacity is <= 0

Method Detail

add

public boolean add(Object object)
Adds an object to this heap. Same as insert.

Parameters: object the object to add

Returns: true, always

clear

public void clear()
Clears all elements from queue.

get

public Object get()
Returns the priority element. Same as peek.

Returns: the priority element

Throws: BufferUnderflowException if this heap is empty

grow

protected void grow()
Increases the size of the heap to support additional elements

insert

public void insert(Object element)
Inserts an element into queue.

Parameters: element the element to be inserted

isEmpty

public boolean isEmpty()
Tests if queue is empty.

Returns: true if queue is empty; false otherwise.

isFull

public boolean isFull()
Tests if queue is full.

Returns: true if queue is full; false otherwise.

iterator

public Iterator iterator()
Returns an iterator over this heap's elements.

Returns: an iterator over this heap's elements

peek

public Object peek()
Returns the element on top of heap but don't remove it.

Returns: the element at top of heap

Throws: NoSuchElementException if isEmpty() == true

percolateDownMaxHeap

protected void percolateDownMaxHeap(int index)
Percolates element down heap from the position given by the index.

Assumes it is a maximum heap.

Parameters: index the index of the element

percolateDownMinHeap

protected void percolateDownMinHeap(int index)
Percolates element down heap from the position given by the index.

Assumes it is a minimum heap.

Parameters: index the index for the element

percolateUpMaxHeap

protected void percolateUpMaxHeap(int index)
Percolates element up heap from from the position given by the index.

Assume it is a maximum heap.

Parameters: index the index of the element to be percolated up

percolateUpMaxHeap

protected void percolateUpMaxHeap(Object element)
Percolates a new element up heap from the bottom.

Assume it is a maximum heap.

Parameters: element the element

percolateUpMinHeap

protected void percolateUpMinHeap(int index)
Percolates element up heap from the position given by the index.

Assumes it is a minimum heap.

Parameters: index the index of the element to be percolated up

percolateUpMinHeap

protected void percolateUpMinHeap(Object element)
Percolates a new element up heap from the bottom.

Assumes it is a minimum heap.

Parameters: element the element

pop

public Object pop()
Returns the element on top of heap and remove it.

Returns: the element at top of heap

Throws: NoSuchElementException if isEmpty() == true

remove

public Object remove()
Removes the priority element. Same as pop.

Returns: the removed priority element

Throws: BufferUnderflowException if this heap is empty

size

public int size()
Returns the number of elements in this heap.

Returns: the number of elements in this heap

toString

public String toString()
Returns a string representation of this heap. The returned string is similar to those produced by standard JDK collections.

Returns: a string representation of this heap

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