it.unimi.dsi.fastutil.objects
Class ReferenceLinkedOpenHashSet

java.lang.Object
  extended byit.unimi.dsi.fastutil.objects.AbstractReferenceCollection
      extended byit.unimi.dsi.fastutil.objects.AbstractReferenceSet
          extended byit.unimi.dsi.fastutil.objects.AbstractReferenceSortedSet
              extended byit.unimi.dsi.fastutil.objects.ReferenceLinkedOpenHashSet
All Implemented Interfaces:
Cloneable, Collection, Hash, ReferenceCollection, ReferenceSet, ReferenceSortedSet, Serializable, Set, SortedSet

public class ReferenceLinkedOpenHashSet
extends AbstractReferenceSortedSet
implements Serializable, Cloneable, Hash, ReferenceSortedSet

A type-specific linked 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 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.

The enlargement speed is controlled by the growth factor, a positive number. If the growth factor is p, then the table is enlarged each time roughly by a factor 2p/16. By default, p is Hash.DEFAULT_GROWTH_FACTOR, which means that the table is doubled at each enlargement, but one can easily set more or less aggressive policies by calling growthFactor(int) (note that the growth factor is not serialized: deserialized tables gets the default growth factor).

This class implements the interface of a sorted set, so to allow easy access of the iteration order: for instance, you can get the first element in iteration order with first() without having to create an iterator; however, this class partially violates the SortedSet contract because all subset methods throw an exception and comparator() returns always null.

The iterators provided by this class are type-specific list iterators. However, creation of an iterator using a starting point is going to be very expensive, as the chosen starting point must be linearly searched for, unless it is last(), in which case the iterator is created in constant time.

Note that deletions in a linked table require scanning the list until the element to be removed is found. The only exceptions are the first element, the last element, and deletions performed using an iterator.

See Also:
Hash, HashCommon, Serialized Form

Nested Class Summary
 
Nested classes inherited from class it.unimi.dsi.fastutil.Hash
Hash.Strategy
 
Field Summary
static long serialVersionUID
           
 
Fields inherited from interface it.unimi.dsi.fastutil.Hash
DEFAULT_GROWTH_FACTOR, DEFAULT_INITIAL_SIZE, DEFAULT_LOAD_FACTOR, FREE, OCCUPIED, PRIMES, REMOVED
 
Constructor Summary
ReferenceLinkedOpenHashSet()
          Creates a new hash set with Hash.DEFAULT_INITIAL_SIZE elements and Hash.DEFAULT_LOAD_FACTOR as load factor.
ReferenceLinkedOpenHashSet(Collection c)
          Creates a new hash set with Hash.DEFAULT_LOAD_FACTOR as load factor copying a given collection.
ReferenceLinkedOpenHashSet(Collection c, float f)
          Creates a new hash set copying a given collection.
ReferenceLinkedOpenHashSet(int n)
          Creates a new hash set with Hash.DEFAULT_LOAD_FACTOR as load factor.
ReferenceLinkedOpenHashSet(int n, float f)
          Creates a new hash set.
ReferenceLinkedOpenHashSet(Object[] a)
          Creates a new hash set with Hash.DEFAULT_LOAD_FACTOR as load factor copying the elements of an array.
ReferenceLinkedOpenHashSet(Object[] a, float f)
          Creates a new set copying the elements of an array.
ReferenceLinkedOpenHashSet(Object[] 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.
ReferenceLinkedOpenHashSet(Object[] a, int offset, int length, float f)
          Creates a new hash set and fills it with the elements of a given array.
ReferenceLinkedOpenHashSet(ObjectIterator i)
          Creates a new hash set with Hash.DEFAULT_LOAD_FACTOR as load factor using elements provided by a type-specific iterator.
ReferenceLinkedOpenHashSet(ObjectIterator i, float f)
          Creates a new hash set using elements provided by a type-specific iterator.
ReferenceLinkedOpenHashSet(ReferenceCollection c)
          Creates a new hash set with Hash.DEFAULT_LOAD_FACTOR as load factor copying a given type-specific collection.
ReferenceLinkedOpenHashSet(ReferenceCollection c, float f)
          Creates a new hash set copying a given type-specific collection.
 
Method Summary
 boolean add(Object k)
           
 void clear()
           
 Object clone()
          Returns a deep copy of this set.
 Comparator comparator()
           
 boolean contains(Object k)
           
 Object first()
          Returns the first element of this set in iteration order.
 int growthFactor()
          Gets the growth factor.
 void growthFactor(int growthFactor)
          Sets the growth factor.
 int hashCode()
          Returns a hash code for this set.
 SortedSet headSet(Object to)
          Delegates to the corresponding type-specific method.
 boolean isEmpty()
           
 ObjectBidirectionalIterator iterator(Object from)
          Returns a type-specific list iterator on the elements in this set, starting from a given element of the set.
 Object last()
          Returns the last element of this set in iteration order.
 ObjectIterator objectIterator()
          Returns a type-specific list iterator on the elements in this set, starting from the first element.
 boolean rehash()
          Rehashes this set without changing the table size.
 boolean remove(Object k)
          Note that the corresponding method of the type-specific collection is rem().
 int size()
           
 SortedSet subSet(Object from, Object to)
          Delegates to the corresponding type-specific method.
 SortedSet tailSet(Object from)
          Delegates to the corresponding type-specific method.
 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.objects.AbstractReferenceSet
equals, rem
 
Methods inherited from class it.unimi.dsi.fastutil.objects.AbstractReferenceCollection
addAll, containsAll, iterator, removeAll, retainAll, toArray, toArray, toString
 
Methods inherited from class java.lang.Object
getClass, notify, notifyAll, wait, wait, wait
 
Methods inherited from interface java.util.Set
addAll, containsAll, equals, iterator, removeAll, retainAll, toArray, toArray
 

Field Detail

serialVersionUID

public static final long serialVersionUID
See Also:
Constant Field Values
Constructor Detail

ReferenceLinkedOpenHashSet

public ReferenceLinkedOpenHashSet(int n,
                                  float f)
Creates a new hash set. The actual table size is the least available prime greater than n/f.

Parameters:
n - the expected number of elements in the hash set.
f - the load factor.
See Also:
Hash.PRIMES

ReferenceLinkedOpenHashSet

public ReferenceLinkedOpenHashSet(int n)
Creates a new hash set with Hash.DEFAULT_LOAD_FACTOR as load factor.

Parameters:
n - the expected number of elements in the hash set.

ReferenceLinkedOpenHashSet

public ReferenceLinkedOpenHashSet()
Creates a new hash set with Hash.DEFAULT_INITIAL_SIZE elements and Hash.DEFAULT_LOAD_FACTOR as load factor.


ReferenceLinkedOpenHashSet

public ReferenceLinkedOpenHashSet(Collection 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.

ReferenceLinkedOpenHashSet

public ReferenceLinkedOpenHashSet(Collection 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.

ReferenceLinkedOpenHashSet

public ReferenceLinkedOpenHashSet(ReferenceCollection 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.

ReferenceLinkedOpenHashSet

public ReferenceLinkedOpenHashSet(ReferenceCollection 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.

ReferenceLinkedOpenHashSet

public ReferenceLinkedOpenHashSet(ObjectIterator 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.

ReferenceLinkedOpenHashSet

public ReferenceLinkedOpenHashSet(ObjectIterator 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.

ReferenceLinkedOpenHashSet

public ReferenceLinkedOpenHashSet(Object[] 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.

ReferenceLinkedOpenHashSet

public ReferenceLinkedOpenHashSet(Object[] 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.

ReferenceLinkedOpenHashSet

public ReferenceLinkedOpenHashSet(Object[] a,
                                  float f)
Creates a new set copying the elements of an array.

Parameters:
a - an array to be copied into the new hash set.
f - the load factor.

ReferenceLinkedOpenHashSet

public ReferenceLinkedOpenHashSet(Object[] 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

growthFactor

public void growthFactor(int growthFactor)
Sets the growth factor. Subsequent enlargements will increase the table size roughly by a multiplicative factor of 2p/16.

Parameters:
growthFactor - the new growth factor; it must be positive.

growthFactor

public int growthFactor()
Gets the growth factor.

Returns:
the growth factor of this set.
See Also:
growthFactor(int)

add

public boolean add(Object k)
Specified by:
add in interface Set
Overrides:
add in class AbstractReferenceCollection

remove

public boolean remove(Object k)
Description copied from interface: ReferenceSet
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 ReferenceSet
Overrides:
remove in class AbstractReferenceSet

contains

public boolean contains(Object k)
Specified by:
contains in interface Set

clear

public void clear()
Specified by:
clear in interface Set
Overrides:
clear in class AbstractReferenceCollection

first

public Object first()
Returns the first element of this set in iteration order.

Specified by:
first in interface SortedSet
Overrides:
first in class AbstractReferenceSortedSet
Returns:
the first element in iteration order.

last

public Object last()
Returns the last element of this set in iteration order.

Specified by:
last in interface SortedSet
Overrides:
last in class AbstractReferenceSortedSet
Returns:
the last element in iteration order.

tailSet

public SortedSet tailSet(Object from)
Description copied from class: AbstractReferenceSortedSet
Delegates to the corresponding type-specific method.

Specified by:
tailSet in interface SortedSet
Overrides:
tailSet in class AbstractReferenceSortedSet

headSet

public SortedSet headSet(Object to)
Description copied from class: AbstractReferenceSortedSet
Delegates to the corresponding type-specific method.

Specified by:
headSet in interface SortedSet
Overrides:
headSet in class AbstractReferenceSortedSet

subSet

public SortedSet subSet(Object from,
                        Object to)
Description copied from class: AbstractReferenceSortedSet
Delegates to the corresponding type-specific method.

Specified by:
subSet in interface SortedSet
Overrides:
subSet in class AbstractReferenceSortedSet

comparator

public Comparator comparator()
Specified by:
comparator in interface SortedSet

iterator

public ObjectBidirectionalIterator iterator(Object from)
Returns a type-specific list iterator on the elements in this set, starting from a given element of the set.

This method provides an iterator positioned immediately after the given element. That is, the next call to previous() will return from, whereas the next call to next() will return the element immediately after from. This allows to call iterator(last()) and obtain an iterator starting from the end of the iteration order.

Because of the way linking is implemented, generating an iterator using this method requires constant time only if the argument is last(). In all other cases, a linear search for the given element will be necessary.

Note that this method returns a bidirectional iterator, which, however, can be safely cast to a type-specific list iterator.

Specified by:
iterator in interface ReferenceSortedSet
Overrides:
iterator in class AbstractReferenceSet
Parameters:
from - an element to start from.
Returns:
a type-specific list iterator starting at the given element.
Throws:
IllegalArgumentException - if from does not belong to the set.

objectIterator

public ObjectIterator objectIterator()
Returns a type-specific list iterator on the elements in this set, starting from the first element.

Note that this method returns a bidirectional iterator, which, however, can be safely cast to a type-specific list iterator.

Specified by:
objectIterator in interface ReferenceCollection
Returns:
a type-specific list iterator.
See Also:
Collection.iterator()

rehash

public boolean rehash()
Rehashes this set without changing the table size.

This method should be called when the set underwent numerous deletions and insertions. In this case, free entries become rare, and unsuccessful searches require probing all entries. For reasonable load factors this method is linear in the number of entries. You will need as much additional free memory as that occupied by the table.

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

Returns:
true if there was enough memory to rehash the set, false otherwise.
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 optimise access speed (by collecting deleted entries) and size.

If the table size is already the minimum possible, this method does nothing. If you want to guarantee rehashing, use rehash().

Returns:
true if there was enough memory to trim the set.
See Also:
trim(int), rehash()

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()

size

public int size()
Specified by:
size in interface Set

isEmpty

public boolean isEmpty()
Specified by:
isEmpty in interface Set
Overrides:
isEmpty in class AbstractReferenceCollection

clone

public Object 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.

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 Set
Overrides:
hashCode in class AbstractReferenceSet
Returns:
a hash code for this set.