Package it.unimi.dsi.fastutil.bytes

Class ByteLinkedOpenCustomHashSet

java.lang.Object
java.util.AbstractCollection<Byte>
it.unimi.dsi.fastutil.bytes.AbstractByteCollection
it.unimi.dsi.fastutil.bytes.AbstractByteSet
it.unimi.dsi.fastutil.bytes.AbstractByteSortedSet
it.unimi.dsi.fastutil.bytes.ByteLinkedOpenCustomHashSet
All Implemented Interfaces:
ByteBidirectionalIterable, ByteCollection, ByteIterable, ByteSet, ByteSortedSet, Hash, Serializable, Cloneable, Iterable<Byte>, Collection<Byte>, SequencedCollection<Byte>, SequencedSet<Byte>, Set<Byte>, SortedSet<Byte>
public class ByteLinkedOpenCustomHashSet extends AbstractByteSortedSet implements Serializable, Cloneable, Hash
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 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.

Iterators generated by this set will enumerate elements in the same order in which they have been added to the set (addition of elements already present in the set does not change the iteration order). Note that this order has nothing in common with the natural order of the keys. The order is kept by means of a doubly linked list, represented via an array of longs parallel to the table.

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.

Additional methods, such as addAndMoveToFirst(), make it easy to use instances of this class as a cache (e.g., with LRU policy).

The iterators provided by this class are type-specific list iterators, and can be started at any element which is in the set (if the provided element is not in the set, a NoSuchElementException exception will be thrown). If, however, the provided element is not the first or last element in the set, the first access to the list index will require linear time, as in the worst case the entire set must be scanned in iteration order to retrieve the positional index of the starting element. If you use just the methods of a type-specific BidirectionalIterator, however, all operations will be performed in constant time.

See Also:

  • Constructor Details

    • ByteLinkedOpenCustomHashSet

      public ByteLinkedOpenCustomHashSet(int expected, float f, ByteHash.Strategy strategy)
      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.
      strategy - the strategy.

    • ByteLinkedOpenCustomHashSet

      public ByteLinkedOpenCustomHashSet(int expected, ByteHash.Strategy strategy)
      Creates a new hash set with Hash.DEFAULT_LOAD_FACTOR as load factor.
      Parameters:
      expected - the expected number of elements in the hash set.
      strategy - the strategy.

    • ByteLinkedOpenCustomHashSet

      public ByteLinkedOpenCustomHashSet(ByteHash.Strategy strategy)
      Creates a new hash set with initial expected Hash.DEFAULT_INITIAL_SIZE elements and Hash.DEFAULT_LOAD_FACTOR as load factor.
      Parameters:
      strategy - the strategy.

    • ByteLinkedOpenCustomHashSet

      public ByteLinkedOpenCustomHashSet(Collection<? extends Byte> c, float f, ByteHash.Strategy strategy)
      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.
      strategy - the strategy.

    • ByteLinkedOpenCustomHashSet

      public ByteLinkedOpenCustomHashSet(Collection<? extends Byte> c, ByteHash.Strategy strategy)
      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.
      strategy - the strategy.

    • ByteLinkedOpenCustomHashSet

      public ByteLinkedOpenCustomHashSet(ByteCollection c, float f, ByteHash.Strategy strategy)
      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.
      strategy - the strategy.

    • ByteLinkedOpenCustomHashSet

      public ByteLinkedOpenCustomHashSet(ByteCollection c, ByteHash.Strategy strategy)
      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.
      strategy - the strategy.

    • ByteLinkedOpenCustomHashSet

      public ByteLinkedOpenCustomHashSet(ByteIterator i, float f, ByteHash.Strategy strategy)
      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.
      strategy - the strategy.

    • ByteLinkedOpenCustomHashSet

      public ByteLinkedOpenCustomHashSet(ByteIterator i, ByteHash.Strategy strategy)
      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.
      strategy - the strategy.

    • ByteLinkedOpenCustomHashSet

      public ByteLinkedOpenCustomHashSet(Iterator<?> i, float f, ByteHash.Strategy strategy)
      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.
      strategy - the strategy.

    • ByteLinkedOpenCustomHashSet

      public ByteLinkedOpenCustomHashSet(Iterator<?> i, ByteHash.Strategy strategy)
      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.
      strategy - the strategy.

    • ByteLinkedOpenCustomHashSet

      public ByteLinkedOpenCustomHashSet(byte[] a, int offset, int length, float f, ByteHash.Strategy strategy)
      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.
      strategy - the strategy.

    • ByteLinkedOpenCustomHashSet

      public ByteLinkedOpenCustomHashSet(byte[] a, int offset, int length, ByteHash.Strategy strategy)
      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.
      strategy - the strategy.

    • ByteLinkedOpenCustomHashSet

      public ByteLinkedOpenCustomHashSet(byte[] a, float f, ByteHash.Strategy strategy)
      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.
      strategy - the strategy.

    • ByteLinkedOpenCustomHashSet

      public ByteLinkedOpenCustomHashSet(byte[] a, ByteHash.Strategy strategy)
      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.
      strategy - the strategy.

  • Method Details

    • strategy

      public ByteHash.Strategy strategy()
      Returns the hashing strategy.
      Returns:
      the hashing strategy of this custom hash set.

    • ensureCapacity

      public void ensureCapacity(int capacity)
      Ensures that this 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(ByteCollection c)
      Description copied from interface: ByteCollection
      Adds all elements of the given type-specific collection to this collection.
      Specified by:
      addAll in interface ByteCollection
      Overrides:
      addAll in class AbstractByteCollection
      Parameters:
      c - a type-specific collection.
      Returns:
      true if this collection changed as a result of the call.
      See Also:

    • addAll

      public boolean addAll(Collection<? extends Byte> c)
      Description copied from class: AbstractByteCollection
      Specified by:
      addAll in interface Collection<Byte>
      Specified by:
      addAll in interface Set<Byte>
      Overrides:
      addAll in class AbstractByteCollection

    • add

      public boolean add(byte k)
      Description copied from class: AbstractByteCollection
      Ensures that this collection contains the specified element (optional operation).
      Specified by:
      add in interface ByteCollection
      Overrides:
      add in class AbstractByteCollection
      See Also:

    • remove

      public boolean remove(byte k)
      Description copied from class: AbstractByteSet
      Removes an element from this set. Delegates to the type-specific rem() method implemented by type-specific abstract Collection superclass.
      Specified by:
      remove in interface ByteSet
      Overrides:
      remove in class AbstractByteSet
      See Also:

    • contains

      public boolean contains(byte k)
      Description copied from class: AbstractByteCollection
      Returns true if this collection contains the specified element.
      Specified by:
      contains in interface ByteCollection
      Overrides:
      contains in class AbstractByteCollection
      See Also:

    • removeFirstByte

      public byte removeFirstByte()
      Removes the first key in iteration order.
      Returns:
      the first key.
      Throws:
      NoSuchElementException - is this set is empty.

    • removeLastByte

      public byte removeLastByte()
      Removes the the last key in iteration order.
      Returns:
      the last key.
      Throws:
      NoSuchElementException - is this set is empty.

    • addAndMoveToFirst

      public boolean addAndMoveToFirst(byte k)
      Adds a key to the set; if the key is already present, it is moved to the first position of the iteration order.
      Parameters:
      k - the key.
      Returns:
      true if the key was not present.

    • addAndMoveToLast

      public boolean addAndMoveToLast(byte k)
      Adds a key to the set; if the key is already present, it is moved to the last position of the iteration order.
      Parameters:
      k - the key.
      Returns:
      true if the key was not present.

    • clear

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

    • size

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

    • isEmpty

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

    • firstByte

      public byte firstByte()
      Returns the first element of this set in iteration order.
      Specified by:
      firstByte in interface ByteSortedSet
      Returns:
      the first element in iteration order.
      See Also:

    • lastByte

      public byte lastByte()
      Returns the last element of this set in iteration order.
      Specified by:
      lastByte in interface ByteSortedSet
      Returns:
      the last element in iteration order.
      See Also:

    • tailSet

      public ByteSortedSet tailSet(byte from)
      Returns a view of the portion of this sorted set whose elements are greater than or equal to fromElement.
      Specified by:
      tailSet in interface ByteSortedSet
      See Also:
      Implementation Specification:
      This implementation just throws an UnsupportedOperationException.

    • headSet

      public ByteSortedSet headSet(byte to)
      Returns a view of the portion of this sorted set whose elements are strictly less than toElement.
      Specified by:
      headSet in interface ByteSortedSet
      See Also:
      Implementation Specification:
      This implementation just throws an UnsupportedOperationException.

    • subSet

      public ByteSortedSet subSet(byte from, byte to)
      Returns a view of the portion of this sorted set whose elements range from fromElement, inclusive, to toElement, exclusive.
      Specified by:
      subSet in interface ByteSortedSet
      See Also:
      Implementation Specification:
      This implementation just throws an UnsupportedOperationException.

    • comparator

      public ByteComparator comparator()
      Specified by:
      comparator in interface ByteSortedSet
      Specified by:
      comparator in interface SortedSet<Byte>
      Implementation Specification:
      This implementation just returns null.

    • iterator

      public ByteListIterator iterator(byte from)
      Returns a type-specific list iterator on the elements in this set, starting from a given element of the set. Please see the class documentation for implementation details.
      Specified by:
      iterator in interface ByteSortedSet
      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.

    • iterator

      public ByteListIterator iterator()
      Returns a type-specific list iterator on the elements in this set, starting from the first element. Please see the class documentation for implementation details.
      Specified by:
      iterator in interface ByteBidirectionalIterable
      Specified by:
      iterator in interface ByteCollection
      Specified by:
      iterator in interface ByteIterable
      Specified by:
      iterator in interface ByteSet
      Specified by:
      iterator in interface ByteSortedSet
      Specified by:
      iterator in interface Collection<Byte>
      Specified by:
      iterator in interface Iterable<Byte>
      Specified by:
      iterator in interface Set<Byte>
      Specified by:
      iterator in class AbstractByteSortedSet
      Returns:
      a type-specific list iterator starting at the first element.
      See Also:

    • spliterator

      public ByteSpliterator spliterator()
      Returns a type-specific spliterator on the elements of this sorted-set.

      SortedSet spliterators must report at least Spliterator.DISTINCT, Spliterator.ORDERED, and Spliterator.SORTED. The returned spliterator's getComparator() must be the same (or at the very least, consistent with) this instance's ByteSortedSet.comparator().

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

      There isn't a way to split efficiently while still preserving order for a linked data structure, so this implementation is just backed by the iterator. Thus, this spliterator is not well optimized for parallel streams.

      Note, contrary to the specification of SortedSet, this spliterator does not, report Spliterator.SORTED. This is because iteration order is based on insertion order, not natural ordering.

      Specified by:
      spliterator in interface ByteCollection
      Specified by:
      spliterator in interface ByteIterable
      Specified by:
      spliterator in interface ByteSet
      Specified by:
      spliterator in interface ByteSortedSet
      Specified by:
      spliterator in interface Collection<Byte>
      Specified by:
      spliterator in interface Iterable<Byte>
      Specified by:
      spliterator in interface Set<Byte>
      Specified by:
      spliterator in interface SortedSet<Byte>
      Returns:
      a type-specific spliterator on the elements of this collection.

    • forEach

      public void forEach(ByteConsumer action)
      Description copied from interface: ByteIterable
      Performs the given action for each element of this type-specific Iterable until all elements have been processed or the action throws an exception.
      Specified by:
      forEach in interface ByteIterable
      Parameters:
      action - the action to be performed for each element.
      See Also:

    • 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(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:

    • clone

      public ByteLinkedOpenCustomHashSet 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 Collection<Byte>
      Specified by:
      hashCode in interface Set<Byte>
      Overrides:
      hashCode in class AbstractByteSet
      Returns:
      a hash code for this set.