it.unimi.dsi.fastutil.chars

Class CharOpenHashSet

java.lang.Object

java.util.AbstractCollection<Character>

it.unimi.dsi.fastutil.chars.AbstractCharCollection

it.unimi.dsi.fastutil.chars.AbstractCharSet

it.unimi.dsi.fastutil.chars.CharOpenHashSet

All Implemented Interfaces:

CharCollection, CharIterable, CharSet, Hash, Serializable, Cloneable, Iterable<Character>, Collection<Character>, Set<Character>

public class CharOpenHashSet
extends AbstractCharSet
implements Serializable, Cloneable, Hash

A type-specific hash set with with a fast, small-footprint implementation.

Instances of this class use a hash table to represent a set. The table is enlarged as needed by doubling its size when new entries are created, but it is never made smaller (even on a clear()). A family of trimming methods lets you control the size of the table; this is particularly useful if you reuse instances of this class.

Warning: The implementation of this class has significantly changed in fastutil 6.1.0. Please read the comments about this issue in the section “Faster Hash Tables” of the overview.

See Also:

Hash, HashCommon, Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from interface it.unimi.dsi.fastutil.Hash

Hash.Strategy<K>

Field Summary

Fields

Modifier and Type	Field and Description
protected float	f The acceptable load factor.
protected char[]	key The array of keys.
protected int	mask The mask for wrapping a position counter.
protected int	maxFill Threshold after which we rehash.
protected int	n The current table size.
static long	serialVersionUID
protected int	size Number of entries in the set.
protected boolean[]	used The array telling whether a position is used.

Fields inherited from interface it.unimi.dsi.fastutil.Hash

DEFAULT_GROWTH_FACTOR, DEFAULT_INITIAL_SIZE, DEFAULT_LOAD_FACTOR, FAST_LOAD_FACTOR, FREE, OCCUPIED, PRIMES, REMOVED, VERY_FAST_LOAD_FACTOR

Constructor Summary

Constructors

Constructor and Description
CharOpenHashSet() Creates a new hash set with initial expected Hash.DEFAULT_INITIAL_SIZE elements and Hash.DEFAULT_LOAD_FACTOR as load factor.
CharOpenHashSet(char[] a) Creates a new hash set with Hash.DEFAULT_LOAD_FACTOR as load factor copying the elements of an array.
CharOpenHashSet(char[] a, float f) Creates a new hash set copying the elements of an array.
CharOpenHashSet(char[] a, int offset, int length) Creates a new hash set with Hash.DEFAULT_LOAD_FACTOR as load factor and fills it with the elements of a given array.
CharOpenHashSet(char[] a, int offset, int length, float f) Creates a new hash set and fills it with the elements of a given array.
CharOpenHashSet(CharCollection c) Creates a new hash set with Hash.DEFAULT_LOAD_FACTOR as load factor copying a given type-specific collection.
CharOpenHashSet(CharCollection c, float f) Creates a new hash set copying a given type-specific collection.
CharOpenHashSet(CharIterator i) Creates a new hash set with Hash.DEFAULT_LOAD_FACTOR as load factor using elements provided by a type-specific iterator.
CharOpenHashSet(CharIterator i, float f) Creates a new hash set using elements provided by a type-specific iterator.
CharOpenHashSet(Collection<? extends Character> c) Creates a new hash set with Hash.DEFAULT_LOAD_FACTOR as load factor copying a given collection.
CharOpenHashSet(Collection<? extends Character> c, float f) Creates a new hash set copying a given collection.
CharOpenHashSet(int expected) Creates a new hash set with Hash.DEFAULT_LOAD_FACTOR as load factor.
CharOpenHashSet(int expected, float f) Creates a new hash set.
CharOpenHashSet(Iterator<?> i) Creates a new hash set with Hash.DEFAULT_LOAD_FACTOR as load factor using elements provided by an iterator.
CharOpenHashSet(Iterator<?> i, float f) Creates a new hash set using elements provided by an iterator.

Method Summary

Methods

Modifier and Type	Method and Description
boolean	add(char k)
void	clear()
CharOpenHashSet	clone() Returns a deep copy of this set.
boolean	contains(char k)
int	growthFactor() Deprecated. Since fastutil 6.1.0, hash tables are doubled when they are too full.
void	growthFactor(int growthFactor) Deprecated. Since fastutil 6.1.0, hash tables are doubled when they are too full.
int	hashCode() Returns a hash code for this set.
boolean	isEmpty()
CharIterator	iterator() Returns a type-specific iterator on the elements of this collection.
boolean	rehash() Deprecated. A no-op.
protected void	rehash(int newN) Resizes the set.
boolean	remove(char k) Removes an element from this set.
protected int	shiftKeys(int pos) Shifts left entries with the specified hash code, starting at the specified position, and empties the resulting free entry.
int	size()
boolean	trim() Rehashes this set, making the table as small as possible.
boolean	trim(int n) Rehashes this set if the table is too large.

Methods inherited from class it.unimi.dsi.fastutil.chars.AbstractCharSet

equals, rem, remove

Methods inherited from class it.unimi.dsi.fastutil.chars.AbstractCharCollection

add, addAll, addAll, charIterator, contains, containsAll, containsAll, rem, removeAll, removeAll, retainAll, retainAll, toArray, toArray, toArray, toCharArray, toCharArray, toString

Methods inherited from class java.lang.Object

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

Methods inherited from interface it.unimi.dsi.fastutil.chars.CharCollection

addAll, charIterator, containsAll, removeAll, retainAll, toArray, toArray, toCharArray, toCharArray

Methods inherited from interface java.util.Set

add, addAll, contains, containsAll, removeAll, retainAll, toArray, toArray

Field Detail

serialVersionUID

public static final long serialVersionUID

See Also:

Constant Field Values

key

protected transient char[] key

The array of keys.

used

protected transient boolean[] used

The array telling whether a position is used.

f

protected final float f

The acceptable load factor.

n

protected transient int n

The current table size.

maxFill

protected transient int maxFill

Threshold after which we rehash. It must be the table size times f.

mask

protected transient int mask

The mask for wrapping a position counter.

size

protected int size

Number of entries in the set.

Constructor Detail

CharOpenHashSet

public CharOpenHashSet(int expected,
               float f)

Creates a new hash set.

The actual table size will be the least power of two greater than expected/f.

Parameters:

expected - the expected number of elements in the hash set.

f - the load factor.

CharOpenHashSet

public CharOpenHashSet(int expected)

Creates a new hash set with Hash.DEFAULT_LOAD_FACTOR as load factor.

Parameters:

expected - the expected number of elements in the hash set.

CharOpenHashSet

public CharOpenHashSet()

Creates a new hash set with initial expected Hash.DEFAULT_INITIAL_SIZE elements and Hash.DEFAULT_LOAD_FACTOR as load factor.

CharOpenHashSet

public CharOpenHashSet(Collection<? extends Character> c,
               float f)

Creates a new hash set copying a given collection.

Parameters:

c - a Collection to be copied into the new hash set.

f - the load factor.

CharOpenHashSet

public CharOpenHashSet(Collection<? extends Character> c)

Creates a new hash set with Hash.DEFAULT_LOAD_FACTOR as load factor copying a given collection.

Parameters:

c - a Collection to be copied into the new hash set.

CharOpenHashSet

public CharOpenHashSet(CharCollection c,
               float f)

Creates a new hash set copying a given type-specific collection.

Parameters:

c - a type-specific collection to be copied into the new hash set.

f - the load factor.

CharOpenHashSet

public CharOpenHashSet(CharCollection c)

Creates a new hash set with Hash.DEFAULT_LOAD_FACTOR as load factor copying a given type-specific collection.

Parameters:

c - a type-specific collection to be copied into the new hash set.

CharOpenHashSet

public CharOpenHashSet(CharIterator i,
               float f)

Creates a new hash set using elements provided by a type-specific iterator.

Parameters:

i - a type-specific iterator whose elements will fill the set.

f - the load factor.

CharOpenHashSet

public CharOpenHashSet(CharIterator i)

Creates a new hash set with Hash.DEFAULT_LOAD_FACTOR as load factor using elements provided by a type-specific iterator.

Parameters:

i - a type-specific iterator whose elements will fill the set.

CharOpenHashSet

public CharOpenHashSet(Iterator<?> i,
               float f)

Creates a new hash set using elements provided by an iterator.

Parameters:

i - an iterator whose elements will fill the set.

f - the load factor.

CharOpenHashSet

public CharOpenHashSet(Iterator<?> i)

Creates a new hash set with Hash.DEFAULT_LOAD_FACTOR as load factor using elements provided by an iterator.

Parameters:

i - an iterator whose elements will fill the set.

CharOpenHashSet

public CharOpenHashSet(char[] a,
               int offset,
               int length,
               float f)

Creates a new hash set and fills it with the elements of a given array.

Parameters:

a - an array whose elements will be used to fill the set.

offset - the first element to use.

length - the number of elements to use.

f - the load factor.

CharOpenHashSet

public CharOpenHashSet(char[] a,
               int offset,
               int length)

Creates a new hash set with Hash.DEFAULT_LOAD_FACTOR as load factor and fills it with the elements of a given array.

Parameters:

a - an array whose elements will be used to fill the set.

offset - the first element to use.

length - the number of elements to use.

CharOpenHashSet

public CharOpenHashSet(char[] a,
               float f)

Creates a new hash set copying the elements of an array.

Parameters:

a - an array to be copied into the new hash set.

f - the load factor.

CharOpenHashSet

public CharOpenHashSet(char[] a)

Creates a new hash set with Hash.DEFAULT_LOAD_FACTOR as load factor copying the elements of an array.

Parameters:

a - an array to be copied into the new hash set.

Method Detail

add

public boolean add(char k)

Specified by:

add in interface CharCollection

Overrides:

add in class AbstractCharCollection

See Also:

Collection.add(Object)

shiftKeys

protected final int shiftKeys(int pos)

Shifts left entries with the specified hash code, starting at the specified position, and empties the resulting free entry.

Parameters:

pos - a starting position.

Returns:

the position cleared by the shifting process.

remove

public boolean remove(char k)

Description copied from interface: CharSet

Removes an element from this set.

Note that the corresponding method of the type-specific collection is rem(). This unfortunate situation is caused by the clash with the similarly named index-based method in the List interface.

Specified by:

remove in interface CharSet

Overrides:

remove in class AbstractCharSet

See Also:

Collection.remove(Object)

contains

public boolean contains(char k)

Specified by:

contains in interface CharCollection

Overrides:

contains in class AbstractCharCollection

See Also:

Collection.contains(Object)

clear

public void clear()

Specified by:

clear in interface Collection<Character>

Specified by:

clear in interface Set<Character>

Overrides:

clear in class AbstractCollection<Character>

size

public int size()

Specified by:

size in interface Collection<Character>

Specified by:

size in interface Set<Character>

Specified by:

size in class AbstractCollection<Character>

isEmpty

public boolean isEmpty()

Specified by:

isEmpty in interface Collection<Character>

Specified by:

isEmpty in interface Set<Character>

Overrides:

isEmpty in class AbstractCharCollection

growthFactor

@Deprecated
public void growthFactor(int growthFactor)

Deprecated. Since fastutil 6.1.0, hash tables are doubled when they are too full.

A no-op for backward compatibility.

Parameters:

growthFactor - unused.

growthFactor

@Deprecated
public int growthFactor()

Deprecated. Since fastutil 6.1.0, hash tables are doubled when they are too full.

Gets the growth factor (2).

Returns:

the growth factor of this set, which is fixed (2).

See Also:

growthFactor(int)

iterator

public CharIterator iterator()

Description copied from interface: CharCollection

Returns a type-specific iterator on the elements of this collection.

Note that this specification strengthens the one given in Iterable.iterator(), which was already strengthened in the corresponding type-specific class, but was weakened by the fact that this interface extends Collection.

Specified by:

iterator in interface CharCollection

Specified by:

iterator in interface CharIterable

Specified by:

iterator in interface CharSet

Specified by:

iterator in interface Iterable<Character>

Specified by:

iterator in interface Collection<Character>

Specified by:

iterator in interface Set<Character>

Specified by:

iterator in class AbstractCharSet

Returns:

a type-specific iterator on the elements of this collection.

rehash

@Deprecated
public boolean rehash()

Deprecated. A no-op.

A no-op for backward compatibility. The kind of tables implemented by this class never need rehashing.

If you need to reduce the table size to fit exactly this set, use trim().

Returns:

true.

See Also:

trim()

trim

public boolean trim()

Rehashes this set, making the table as small as possible.

This method rehashes the table to the smallest size satisfying the load factor. It can be used when the set will not be changed anymore, so to optimize access speed and size.

If the table size is already the minimum possible, this method does nothing.

Returns:

true if there was enough memory to trim the set.

See Also:

trim(int)

trim

public boolean trim(int n)

Rehashes this set if the table is too large.

Let N be the smallest table size that can hold max(n,size()) entries, still satisfying the load factor. If the current table size is smaller than or equal to N, this method does nothing. Otherwise, it rehashes this set in a table of size N.

This method is useful when reusing sets. Clearing a set leaves the table size untouched. If you are reusing a set many times, you can call this method with a typical size to avoid keeping around a very large table just because of a few large transient sets.

Parameters:

n - the threshold for the trimming.

Returns:

true if there was enough memory to trim the set.

See Also:

trim()

rehash

protected void rehash(int newN)

Resizes the set.

This method implements the basic rehashing strategy, and may be overriden by subclasses implementing different rehashing strategies (e.g., disk-based rehashing). However, you should not override this method unless you understand the internal workings of this class.

Parameters:

newN - the new size

clone

public CharOpenHashSet clone()

Returns a deep copy of this set.

This method performs a deep copy of this hash set; the data stored in the set, however, is not cloned. Note that this makes a difference only for object keys.

Overrides:

clone in class Object

Returns:

a deep copy of this set.

hashCode

public int hashCode()

Returns a hash code for this set. This method overrides the generic method provided by the superclass. Since equals() is not overriden, it is important that the value returned by this method is the same value as the one returned by the overriden method.

Specified by:

hashCode in interface Collection<Character>

Specified by:

hashCode in interface Set<Character>

Overrides:

hashCode in class AbstractCharSet

Returns:

a hash code for this set.