it.unimi.dsi.fastutil.shorts
Class ShortOpenHashSet

java.lang.Object
  extended by java.util.AbstractCollection<Short>
      extended by it.unimi.dsi.fastutil.shorts.AbstractShortCollection
          extended by it.unimi.dsi.fastutil.shorts.AbstractShortSet
              extended by it.unimi.dsi.fastutil.shorts.ShortOpenHashSet
All Implemented Interfaces:
Hash, ShortCollection, ShortIterable, ShortSet, Serializable, Cloneable, Iterable<Short>, Collection<Short>, Set<Short>

public class ShortOpenHashSet
extends AbstractShortSet
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
protected  float f
          The acceptable load factor.
protected  short[] 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
ShortOpenHashSet()
          Creates a new hash set with initial expected Hash.DEFAULT_INITIAL_SIZE elements and Hash.DEFAULT_LOAD_FACTOR as load factor.
ShortOpenHashSet(Collection<? extends Short> c)
          Creates a new hash set with Hash.DEFAULT_LOAD_FACTOR as load factor copying a given collection.
ShortOpenHashSet(Collection<? extends Short> c, float f)
          Creates a new hash set copying a given collection.
ShortOpenHashSet(int expected)
          Creates a new hash set with Hash.DEFAULT_LOAD_FACTOR as load factor.
ShortOpenHashSet(int expected, float f)
          Creates a new hash set.
ShortOpenHashSet(Iterator<?> i)
          Creates a new hash set with Hash.DEFAULT_LOAD_FACTOR as load factor using elements provided by an iterator.
ShortOpenHashSet(Iterator<?> i, float f)
          Creates a new hash set using elements provided by an iterator.
ShortOpenHashSet(short[] a)
          Creates a new hash set with Hash.DEFAULT_LOAD_FACTOR as load factor copying the elements of an array.
ShortOpenHashSet(short[] a, float f)
          Creates a new hash set copying the elements of an array.
ShortOpenHashSet(short[] 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.
ShortOpenHashSet(short[] a, int offset, int length, float f)
          Creates a new hash set and fills it with the elements of a given array.
ShortOpenHashSet(ShortCollection c)
          Creates a new hash set with Hash.DEFAULT_LOAD_FACTOR as load factor copying a given type-specific collection.
ShortOpenHashSet(ShortCollection c, float f)
          Creates a new hash set copying a given type-specific collection.
ShortOpenHashSet(ShortIterator i)
          Creates a new hash set with Hash.DEFAULT_LOAD_FACTOR as load factor using elements provided by a type-specific iterator.
ShortOpenHashSet(ShortIterator i, float f)
          Creates a new hash set using elements provided by a type-specific iterator.
 
Method Summary
 boolean add(short k)
           
 void clear()
           
 ShortOpenHashSet clone()
          Returns a deep copy of this set.
 boolean contains(short 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()
           
 ShortIterator 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(short 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.shorts.AbstractShortSet
equals, rem, remove
 
Methods inherited from class it.unimi.dsi.fastutil.shorts.AbstractShortCollection
add, addAll, addAll, contains, containsAll, containsAll, rem, removeAll, removeAll, retainAll, retainAll, shortIterator, toArray, toArray, toArray, toShortArray, toShortArray, toString
 
Methods inherited from class java.lang.Object
finalize, getClass, notify, notifyAll, wait, wait, wait
 
Methods inherited from interface it.unimi.dsi.fastutil.shorts.ShortCollection
addAll, containsAll, removeAll, retainAll, shortIterator, toArray, toArray, toShortArray, toShortArray
 
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 short[] 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

ShortOpenHashSet

public ShortOpenHashSet(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.

ShortOpenHashSet

public ShortOpenHashSet(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.

ShortOpenHashSet

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


ShortOpenHashSet

public ShortOpenHashSet(Collection<? extends Short> 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.

ShortOpenHashSet

public ShortOpenHashSet(Collection<? extends Short> 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.

ShortOpenHashSet

public ShortOpenHashSet(ShortCollection 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.

ShortOpenHashSet

public ShortOpenHashSet(ShortCollection 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.

ShortOpenHashSet

public ShortOpenHashSet(ShortIterator 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.

ShortOpenHashSet

public ShortOpenHashSet(ShortIterator 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.

ShortOpenHashSet

public ShortOpenHashSet(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.

ShortOpenHashSet

public ShortOpenHashSet(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.

ShortOpenHashSet

public ShortOpenHashSet(short[] 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.

ShortOpenHashSet

public ShortOpenHashSet(short[] 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.

ShortOpenHashSet

public ShortOpenHashSet(short[] 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.

ShortOpenHashSet

public ShortOpenHashSet(short[] 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(short k)
Specified by:
add in interface ShortCollection
Overrides:
add in class AbstractShortCollection
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(short k)
Description copied from interface: ShortSet
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 ShortSet
Overrides:
remove in class AbstractShortSet
See Also:
Collection.remove(Object)

contains

public boolean contains(short k)
Specified by:
contains in interface ShortCollection
Overrides:
contains in class AbstractShortCollection
See Also:
Collection.contains(Object)

clear

public void clear()
Specified by:
clear in interface Collection<Short>
Specified by:
clear in interface Set<Short>
Overrides:
clear in class AbstractCollection<Short>

size

public int size()
Specified by:
size in interface Collection<Short>
Specified by:
size in interface Set<Short>
Specified by:
size in class AbstractCollection<Short>

isEmpty

public boolean isEmpty()
Specified by:
isEmpty in interface Collection<Short>
Specified by:
isEmpty in interface Set<Short>
Overrides:
isEmpty in class AbstractShortCollection

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 ShortIterator iterator()
Description copied from interface: ShortCollection
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 ShortCollection
Specified by:
iterator in interface ShortIterable
Specified by:
iterator in interface ShortSet
Specified by:
iterator in interface Iterable<Short>
Specified by:
iterator in interface Collection<Short>
Specified by:
iterator in interface Set<Short>
Specified by:
iterator in class AbstractShortSet
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 ShortOpenHashSet 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<Short>
Specified by:
hashCode in interface Set<Short>
Overrides:
hashCode in class AbstractShortSet
Returns:
a hash code for this set.


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