Package it.unimi.dsi.fastutil.longs

Class LongLinkedOpenHashSet

  • All Implemented Interfaces:
    Hash, LongBidirectionalIterable, LongCollection, LongIterable, LongSet, LongSortedSet, Serializable, Cloneable, Iterable<Long>, Collection<Long>, Set<Long>, SortedSet<Long>
    public class LongLinkedOpenHashSet
extends AbstractLongSortedSet
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:
    Hash, HashCommon, Serialized Form

    • Constructor Detail

      • LongLinkedOpenHashSet

        public LongLinkedOpenHashSet​(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.

      • LongLinkedOpenHashSet

        public LongLinkedOpenHashSet​(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.

      • LongLinkedOpenHashSet

        public LongLinkedOpenHashSet​(Collection<? extends Long> 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.

      • LongLinkedOpenHashSet

        public LongLinkedOpenHashSet​(Collection<? extends Long> 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.

      • LongLinkedOpenHashSet

        public LongLinkedOpenHashSet​(LongCollection 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.

      • LongLinkedOpenHashSet

        public LongLinkedOpenHashSet​(LongCollection 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.

      • LongLinkedOpenHashSet

        public LongLinkedOpenHashSet​(LongIterator 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.

      • LongLinkedOpenHashSet

        public LongLinkedOpenHashSet​(LongIterator 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.

      • LongLinkedOpenHashSet

        public LongLinkedOpenHashSet​(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.

      • LongLinkedOpenHashSet

        public LongLinkedOpenHashSet​(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.

      • LongLinkedOpenHashSet

        public LongLinkedOpenHashSet​(long[] 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.

      • LongLinkedOpenHashSet

        public LongLinkedOpenHashSet​(long[] 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.

      • LongLinkedOpenHashSet

        public LongLinkedOpenHashSet​(long[] 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.

      • LongLinkedOpenHashSet

        public LongLinkedOpenHashSet​(long[] 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

      • remove

        public boolean remove​(long k)
        Description copied from class: AbstractLongSet
        Removes an element from this set.

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

        Specified by:
        remove in interface LongSet
        Overrides:
        remove in class AbstractLongSet
        See Also:
        Collection.remove(Object)

      • removeFirstLong

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

      • removeLastLong

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

      • addAndMoveToFirst

        public boolean addAndMoveToFirst​(long 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​(long 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.

      • firstLong

        public long firstLong()
        Returns the first element of this set in iteration order.
        Specified by:
        firstLong in interface LongSortedSet
        Returns:
        the first element in iteration order.
        See Also:
        SortedSet.first()

      • lastLong

        public long lastLong()
        Returns the last element of this set in iteration order.
        Specified by:
        lastLong in interface LongSortedSet
        Returns:
        the last element in iteration order.
        See Also:
        SortedSet.last()

      • iterator

        public LongListIterator iterator​(long 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 LongSortedSet
        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.

      • 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()

      • clone

        public LongLinkedOpenHashSet 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<Long>
        Specified by:
        hashCode in interface Set<Long>
        Overrides:
        hashCode in class AbstractLongSet
        Returns:
        a hash code for this set.