Package net.ontopia.utils

Class CompactHashSet<E>

java.lang.Object

java.util.AbstractCollection<E>

java.util.AbstractSet<E>

net.ontopia.utils.CompactHashSet<E>

All Implemented Interfaces:

Iterable<E>, Collection<E>, Set<E>

Direct Known Subclasses:

CompactIdentityHashSet, SynchronizedCompactHashSet, TreeWidget.UniversalSet, UniqueSet

public class CompactHashSet<E>
extends AbstractSet<E>

INTERNAL: Implements the Set interface more compactly than java.util.HashSet by using a closed hashtable.

Field Summary

Fields

Modifier and Type	Field	Description
protected static Object	deletedObject	When an object is deleted this object is put into the hashtable in its place, so that other objects with the same key (collisions) further down the hashtable are not lost after we delete an object in the collision chain.
protected int	elements
protected int	freecells	This is the number of empty (null) cells.
protected static int	INITIAL_SIZE
protected static double	LOAD_FACTOR
protected int	modCount
protected static Object	nullObject	This object is used to represent null, should clients add that to the set.
protected E[]	objects

Constructor Summary

Constructors

Constructor	Description
CompactHashSet()	Constructs a new, empty set.
CompactHashSet(int size)	Constructs a new, empty set.
CompactHashSet(Collection<E> c)	Constructs a new set containing the elements in the specified collection.

Method Summary

Modifier and Type	Method	Description
boolean	add(Object o)	Adds the specified element to this set if it is not already present.
void	clear()	Removes all of the elements from this set.
boolean	contains(Object o)	Returns true if this set contains the specified element.
void	dump()	INTERNAL: Used for debugging only.
boolean	isEmpty()	Returns true if this set contains no elements.
Iterator<E>	iterator()	Returns an iterator over the elements in this set.
protected void	rehash()	INTERNAL: Figures out correct size for rehashed set, then does the rehash.
protected void	rehash(int newCapacity)	INTERNAL: Rehashes the hashset to a bigger size.
boolean	remove(Object o)	Removes the specified element from the set.
int	size()	Returns the number of elements in this set (its cardinality).
Object[]	toArray()
<T> T[]	toArray(T[] a)

Methods inherited from class java.util.AbstractSet

equals, hashCode, removeAll

Methods inherited from class java.util.AbstractCollection

addAll, containsAll, retainAll, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Collection

parallelStream, removeIf, stream, toArray

Methods inherited from interface java.lang.Iterable

forEach

Methods inherited from interface java.util.Set

addAll, containsAll, retainAll, spliterator

Field Detail

INITIAL_SIZE

protected static final int INITIAL_SIZE

See Also:

Constant Field Values

LOAD_FACTOR

protected static final double LOAD_FACTOR

See Also:

Constant Field Values

nullObject

protected static final Object nullObject

This object is used to represent null, should clients add that to the set.

deletedObject

protected static final Object deletedObject

When an object is deleted this object is put into the hashtable in its place, so that other objects with the same key (collisions) further down the hashtable are not lost after we delete an object in the collision chain.

elements

protected int elements

freecells

protected int freecells

This is the number of empty (null) cells. It's not necessarily the same as objects.length - elements, because some cells may contain deletedObject.

objects

protected E[] objects

modCount

protected int modCount

Constructor Detail

CompactHashSet

public CompactHashSet()

Constructs a new, empty set.

CompactHashSet

public CompactHashSet(int size)

Constructs a new, empty set.

CompactHashSet

public CompactHashSet(Collection<E> c)

Constructs a new set containing the elements in the specified collection.

Parameters:

c - the collection whose elements are to be placed into this set.

Method Detail

iterator

public Iterator<E> iterator()

Returns an iterator over the elements in this set. The elements are returned in no particular order.

Specified by:

iterator in interface Collection<E>

Specified by:

iterator in interface Iterable<E>

Specified by:

iterator in interface Set<E>

Specified by:

iterator in class AbstractCollection<E>

Returns:

an Iterator over the elements in this set.

See Also:

ConcurrentModificationException

size

public int size()

Returns the number of elements in this set (its cardinality).

Specified by:

size in interface Collection<E>

Specified by:

size in interface Set<E>

Specified by:

size in class AbstractCollection<E>

isEmpty

public boolean isEmpty()

Returns true if this set contains no elements.

Specified by:

isEmpty in interface Collection<E>

Specified by:

isEmpty in interface Set<E>

Overrides:

isEmpty in class AbstractCollection<E>

contains

public boolean contains(Object o)

Returns true if this set contains the specified element.

Specified by:

contains in interface Collection<E>

Specified by:

contains in interface Set<E>

Overrides:

contains in class AbstractCollection<E>

Parameters:

o - element whose presence in this set is to be tested.

Returns:

true if this set contains the specified element.

add

public boolean add(Object o)

Adds the specified element to this set if it is not already present.

Specified by:

add in interface Collection<E>

Specified by:

add in interface Set<E>

Overrides:

add in class AbstractCollection<E>

Parameters:

o - element to be added to this set.

Returns:

true if the set did not already contain the specified element.

remove

public boolean remove(Object o)

Removes the specified element from the set.

Specified by:

remove in interface Collection<E>

Specified by:

remove in interface Set<E>

Overrides:

remove in class AbstractCollection<E>

clear

public void clear()

Removes all of the elements from this set.

Specified by:

clear in interface Collection<E>

Specified by:

clear in interface Set<E>

Overrides:

clear in class AbstractCollection<E>

toArray

public Object[] toArray()

Specified by:

toArray in interface Collection<E>

Specified by:

toArray in interface Set<E>

Overrides:

toArray in class AbstractCollection<E>

toArray

public <T> T[] toArray(T[] a)

Specified by:

toArray in interface Collection<E>

Specified by:

toArray in interface Set<E>

Overrides:

toArray in class AbstractCollection<E>

dump

public void dump()

INTERNAL: Used for debugging only.

rehash

protected void rehash()

INTERNAL: Figures out correct size for rehashed set, then does the rehash.

rehash

protected void rehash(int newCapacity)

INTERNAL: Rehashes the hashset to a bigger size.