Package it.unimi.dsi.fastutil.objects

Class ObjectOpenHashBigSet<K>

java.lang.Object
java.util.AbstractCollection<K>
it.unimi.dsi.fastutil.objects.AbstractObjectCollection<K>
it.unimi.dsi.fastutil.objects.AbstractObjectSet<K>
it.unimi.dsi.fastutil.objects.ObjectOpenHashBigSet<K>
All Implemented Interfaces:
Hash, ObjectCollection<K>, ObjectIterable<K>, ObjectSet<K>, Size64, Serializable, Cloneable, Iterable<K>, Collection<K>, Set<K>
public class ObjectOpenHashBigSet<K> extends AbstractObjectSet<K> implements Serializable, Cloneable, Hash, Size64
A type-specific hash big set with with a fast, small-footprint implementation.

Instances of this class use a hash table to represent a big set: the number of elements in the set is limited only by the amount of core memory. The table (backed by a big array) is filled up to a specified load factor, and then doubled in size to accommodate new entries. If the table is emptied below one fourth of the load factor, it is halved in size; however, the table is never reduced to a size smaller than that at creation time: this approach makes it possible to create sets with a large capacity in which insertions and deletions do not cause immediately rehashing. Moreover, halving is not performed when deleting entries from an iterator, as it would interfere with the iteration process.

Note that clear() does not modify the hash table size. Rather, 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 methods of this class are about 30% slower than those of the corresponding non-big set.

See Also:

  • Constructor Details

    • ObjectOpenHashBigSet

      public ObjectOpenHashBigSet(long expected, float f)
      Creates a new hash big 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 set.
      f - the load factor.

    • ObjectOpenHashBigSet

      public ObjectOpenHashBigSet(long expected)
      Creates a new hash big set with Hash.DEFAULT_LOAD_FACTOR as load factor.
      Parameters:
      expected - the expected number of elements in the hash big set.

    • ObjectOpenHashBigSet

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

    • ObjectOpenHashBigSet

      public ObjectOpenHashBigSet(Collection<? extends K> c, float f)
      Creates a new hash big set copying a given collection.
      Parameters:
      c - a Collection to be copied into the new hash big set.
      f - the load factor.

    • ObjectOpenHashBigSet

      public ObjectOpenHashBigSet(Collection<? extends K> c)
      Creates a new hash big set with Hash.DEFAULT_LOAD_FACTOR as load factor copying a given collection.
      Parameters:
      c - a Collection to be copied into the new hash big set.

    • ObjectOpenHashBigSet

      public ObjectOpenHashBigSet(ObjectCollection<? extends K> c, float f)
      Creates a new hash big set copying a given type-specific collection.
      Parameters:
      c - a type-specific collection to be copied into the new hash big set.
      f - the load factor.

    • ObjectOpenHashBigSet

      public ObjectOpenHashBigSet(ObjectCollection<? extends K> c)
      Creates a new hash big 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 big set.

    • ObjectOpenHashBigSet

      public ObjectOpenHashBigSet(Iterator<? extends K> i, float f)
      Creates a new hash big set using elements provided by a type-specific iterator.
      Parameters:
      i - a type-specific iterator whose elements will fill the new hash big set.
      f - the load factor.

    • ObjectOpenHashBigSet

      public ObjectOpenHashBigSet(Iterator<? extends K> i)
      Creates a new hash big 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 new hash big set.

    • ObjectOpenHashBigSet

      public ObjectOpenHashBigSet(K[] a, int offset, int length, float f)
      Creates a new hash big set and fills it with the elements of a given array.
      Parameters:
      a - an array whose elements will be used to fill the new hash big set.
      offset - the first element to use.
      length - the number of elements to use.
      f - the load factor.

    • ObjectOpenHashBigSet

      public ObjectOpenHashBigSet(K[] a, int offset, int length)
      Creates a new hash big 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 new hash big set.
      offset - the first element to use.
      length - the number of elements to use.

    • ObjectOpenHashBigSet

      public ObjectOpenHashBigSet(K[] a, float f)
      Creates a new hash big set copying the elements of an array.
      Parameters:
      a - an array to be copied into the new hash big set.
      f - the load factor.

    • ObjectOpenHashBigSet

      public ObjectOpenHashBigSet(K[] a)
      Creates a new hash big 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 big set.

  • Method Details

    • toBigSet

      public static <K> Collector<K,?,ObjectOpenHashBigSet<K>> toBigSet()
      Returns a Collector that collects a Stream's elements into a new big hash set.

    • toBigSetWithExpectedSize

      public static <K> Collector<K,?,ObjectOpenHashBigSet<K>> toBigSetWithExpectedSize(long expectedSize)
      Returns a Collector that collects a Stream's elements into a new big hash set.

    • ensureCapacity

      public void ensureCapacity(long capacity)
      Ensures that this big set can hold a certain number of elements without rehashing.
      Parameters:
      capacity - a number of elements; there will be no rehashing unless the set size exceeds this number.

    • addAll

      public boolean addAll(Collection<? extends K> c)
      Specified by:
      addAll in interface Collection<K>
      Specified by:
      addAll in interface Set<K>
      Overrides:
      addAll in class AbstractCollection<K>

    • add

      public boolean add(K k)
      Specified by:
      add in interface Collection<K>
      Specified by:
      add in interface Set<K>
      Overrides:
      add in class AbstractCollection<K>

    • addOrGet

      public K addOrGet(K k)
      Add a random element if not present, get the existing value if already present. This is equivalent to (but faster than) doing a: 
       K exist = set.get(k);
 if (exist == null) {
        set.add(k);
        exist = k;
 }

    • remove

      public boolean remove(Object k)
      Specified by:
      remove in interface Collection<K>
      Specified by:
      remove in interface Set<K>
      Overrides:
      remove in class AbstractCollection<K>

    • contains

      public boolean contains(Object k)
      Specified by:
      contains in interface Collection<K>
      Specified by:
      contains in interface Set<K>
      Overrides:
      contains in class AbstractCollection<K>

    • get

      public K get(Object k)
      Returns the element of this set that is equal to the given key, or null.
      Returns:
      the element of this set that is equal to the given key, or null.

    • clear

      public void clear()

      To increase object reuse, this method does not change the table size. If you want to reduce the table size, you must use trim(long).

      Specified by:
      clear in interface Collection<K>
      Specified by:
      clear in interface Set<K>
      Overrides:
      clear in class AbstractCollection<K>

    • iterator

      public ObjectIterator<K> iterator()
      Description copied from interface: ObjectCollection
      Returns a type-specific iterator on the elements of this collection.
      Specified by:
      iterator in interface Collection<K>
      Specified by:
      iterator in interface Iterable<K>
      Specified by:
      iterator in interface ObjectCollection<K>
      Specified by:
      iterator in interface ObjectIterable<K>
      Specified by:
      iterator in interface ObjectSet<K>
      Specified by:
      iterator in interface Set<K>
      Specified by:
      iterator in class AbstractObjectSet<K>
      Returns:
      a type-specific iterator on the elements of this collection.
      See Also:

    • spliterator

      public ObjectSpliterator<K> spliterator()
      Description copied from interface: ObjectSet
      Returns a type-specific spliterator on the elements of this set.

      Set spliterators must report at least Spliterator.DISTINCT.

      See Set.spliterator() for more documentation on the requirements of the returned spliterator.

      Specified by:
      spliterator in interface Collection<K>
      Specified by:
      spliterator in interface Iterable<K>
      Specified by:
      spliterator in interface ObjectCollection<K>
      Specified by:
      spliterator in interface ObjectIterable<K>
      Specified by:
      spliterator in interface ObjectSet<K>
      Specified by:
      spliterator in interface Set<K>
      Returns:
      a type-specific spliterator on the elements of this collection.

    • forEach

      public void forEach(Consumer<? super K> action)
      Specified by:
      forEach in interface Iterable<K>

    • 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

      public boolean trim(long n)
      Rehashes this set if the table is too large.

      Let N be the smallest table size that can hold max(n,size64()) 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:

    • size

      @Deprecated public int size()
      Deprecated.
      Description copied from interface: Size64
      Returns the size of this data structure, minimized with Integer.MAX_VALUE.

      This default implementation follows the definition above, which is compatible with Collection.size().

      Specified by:
      size in interface Collection<K>
      Specified by:
      size in interface Set<K>
      Specified by:
      size in interface Size64
      Specified by:
      size in class AbstractCollection<K>
      Returns:
      the size of this data structure, minimized with Integer.MAX_VALUE.
      See Also:

    • size64

      public long size64()
      Description copied from interface: Size64
      Returns the size of this data structure as a long.
      Specified by:
      size64 in interface Size64
      Returns:
      the size of this data structure.

    • isEmpty

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

    • clone

      public ObjectOpenHashBigSet<K> clone()
      Returns a deep copy of this big set.

      This method performs a deep copy of this big 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 big 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<K>
      Specified by:
      hashCode in interface Set<K>
      Overrides:
      hashCode in class AbstractObjectSet<K>
      Returns:
      a hash code for this set.