Package com.unboundid.util

Class WeakHashSet<T>

  • Type Parameters:
    T - The type of element held in this set.
    All Implemented Interfaces:
    java.lang.Iterable<T>, java.util.Collection<T>, java.util.Set<T>
    @Mutable
@ThreadSafety(level=NOT_THREADSAFE)
public final class WeakHashSet<T>
extends java.lang.Object
implements java.util.Set<T>
    This class provides a weak hash set, which maintains weak references to the elements it contains, so that they will be removed automatically once there are no more normal references to them.

    Note that because this set uses weak references, elements may disappear from the set at any time without being explicitly removed. This means that care must be taken to ensure that the result of one method must not be considered authoritative for subsequent calls to the same method or other methods in this class.

    • Constructor Summary

      Constructors 
      Constructor Description
      WeakHashSet()
      Creates a new weak hash set with the default initial capacity.
      WeakHashSet​(int initialCapacity)
      Creates a new weak hash set with the specified initial capacity.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      boolean add​(T e)
      Adds the provided element to this set, if it does not already exist.
      boolean addAll​(java.util.Collection<? extends T> c)
      Adds any elements from the provided collection to this set if they were not already present.
      T addAndGet​(T e)
      Adds the provided element to the set if it does not already exist, and retrieves the value stored in the set.
      void clear()
      Clears the contents of this set.
      boolean contains​(java.lang.Object e)
      Indicates whether this set contains the specified element.
      boolean containsAll​(java.util.Collection<?> c)
      Indicates whether this set currently contains all of the elements in the provided collection.
      boolean equals​(java.lang.Object o)
      Indicates whether the provided object is equal to this set.
      T get​(T e)
      Retrieves the existing instance of the provided element from this set.
      int hashCode()
      Retrieves a hash code for this set.
      boolean isEmpty()
      Indicates whether this set is currently empty.
      java.util.Iterator<T> iterator()
      Retrieves an iterator across all elements in this set.
      boolean remove​(java.lang.Object e)
      Removes the specified element from this set, if it exists.
      boolean removeAll​(java.util.Collection<?> c)
      Removes all of the elements of the provided collection from this set.
      boolean retainAll​(java.util.Collection<?> c)
      Removes all elements from this set which are not contained in the provided collection.
      int size()
      Retrieves the number of elements currently held in this set.
      java.lang.Object[] toArray()
      Retrieves an array containing all of the elements currently held in this set.
      <E> E[] toArray​(E[] a)
      Retrieves an array containing all of the elements currently held in this set.
      java.lang.String toString()
      Retrieves a string representation of this set.

      • Methods inherited from class java.lang.Object

        clone, finalize, getClass, notify, notifyAll, wait, wait, wait

      • Methods inherited from interface java.util.Collection

        parallelStream, removeIf, stream, toArray

      • Methods inherited from interface java.lang.Iterable

        forEach

      • Methods inherited from interface java.util.Set

        spliterator

    • Constructor Detail

      • WeakHashSet

        public WeakHashSet()
        Creates a new weak hash set with the default initial capacity.

      • WeakHashSet

        public WeakHashSet​(int initialCapacity)
        Creates a new weak hash set with the specified initial capacity.
        Parameters:
        initialCapacity - The initial capacity for this weak hash set. It must not be null.

    • Method Detail

      • clear

        public void clear()
        Clears the contents of this set.
        Specified by:
        clear in interface java.util.Collection<T>
        Specified by:
        clear in interface java.util.Set<T>

      • isEmpty

        public boolean isEmpty()
        Indicates whether this set is currently empty.
        Specified by:
        isEmpty in interface java.util.Collection<T>
        Specified by:
        isEmpty in interface java.util.Set<T>
        Returns:
        true if this set is empty, or false if not.

      • size

        public int size()
        Retrieves the number of elements currently held in this set.
        Specified by:
        size in interface java.util.Collection<T>
        Specified by:
        size in interface java.util.Set<T>
        Returns:
        The number of elements currently held in this set.

      • contains

        public boolean contains​(java.lang.Object e)
        Indicates whether this set contains the specified element.
        Specified by:
        contains in interface java.util.Collection<T>
        Specified by:
        contains in interface java.util.Set<T>
        Parameters:
        e - The element for which to make the determination.
        Returns:
        true if this set contains the specified element, or false if not.

      • containsAll

        public boolean containsAll​(java.util.Collection<?> c)
        Indicates whether this set currently contains all of the elements in the provided collection.
        Specified by:
        containsAll in interface java.util.Collection<T>
        Specified by:
        containsAll in interface java.util.Set<T>
        Parameters:
        c - The collection for which to make the determination.
        Returns:
        true if this set currently contains all of the elements in the provided collection, or false if not.

      • get

        public T get​(T e)
        Retrieves the existing instance of the provided element from this set.
        Parameters:
        e - The object for which to obtain the existing element.
        Returns:
        The existing instance of the provided element, or null if the provided element is not contained in this set.

      • add

        public boolean add​(T e)
        Adds the provided element to this set, if it does not already exist.
        Specified by:
        add in interface java.util.Collection<T>
        Specified by:
        add in interface java.util.Set<T>
        Parameters:
        e - The element to be added to the set if it does not already exist.
        Returns:
        true if the element was added to the set (because it was not already present), or false if the element was not added (because it was already in the set).

      • addAll

        public boolean addAll​(java.util.Collection<? extends T> c)
        Adds any elements from the provided collection to this set if they were not already present.
        Specified by:
        addAll in interface java.util.Collection<T>
        Specified by:
        addAll in interface java.util.Set<T>
        Parameters:
        c - The collection containing elements to add.
        Returns:
        true if at least one of the elements was not already in the set and was added, or false if no elements were added because they were already all present.

      • addAndGet

        public T addAndGet​(T e)
        Adds the provided element to the set if it does not already exist, and retrieves the value stored in the set.
        Parameters:
        e - The element to be added to the set if it does not already exist.
        Returns:
        An existing version of the provided element if it was already in the set, or the provided object if it was just added.

      • remove

        public boolean remove​(java.lang.Object e)
        Removes the specified element from this set, if it exists.
        Specified by:
        remove in interface java.util.Collection<T>
        Specified by:
        remove in interface java.util.Set<T>
        Parameters:
        e - The element to be removed from this set.
        Returns:
        true if the element existed in the set and was removed, or false if not.

      • removeAll

        public boolean removeAll​(java.util.Collection<?> c)
        Removes all of the elements of the provided collection from this set.
        Specified by:
        removeAll in interface java.util.Collection<T>
        Specified by:
        removeAll in interface java.util.Set<T>
        Parameters:
        c - The collection containing the elements to remove from this set.
        Returns:
        true if at least one of the elements from the provided collection were contained in and therefore removed from the set, or false if none of the elements in the given collection were contained in this set.

      • retainAll

        public boolean retainAll​(java.util.Collection<?> c)
        Removes all elements from this set which are not contained in the provided collection.
        Specified by:
        retainAll in interface java.util.Collection<T>
        Specified by:
        retainAll in interface java.util.Set<T>
        Parameters:
        c - The collection of elements to be retained.
        Returns:
        true if this set contained at least one element not in the provided collection that was therefore removed, or false if this set did not have any elements that were not in the provided collection.

      • iterator

        public java.util.Iterator<T> iterator()
        Retrieves an iterator across all elements in this set.
        Specified by:
        iterator in interface java.util.Collection<T>
        Specified by:
        iterator in interface java.lang.Iterable<T>
        Specified by:
        iterator in interface java.util.Set<T>
        Returns:
        An iterator across all elements in this set.

      • toArray

        public java.lang.Object[] toArray()
        Retrieves an array containing all of the elements currently held in this set.
        Specified by:
        toArray in interface java.util.Collection<T>
        Specified by:
        toArray in interface java.util.Set<T>
        Returns:
        An array containing all of the elements currently held in this set.

      • toArray

        public <E> E[] toArray​(E[] a)
        Retrieves an array containing all of the elements currently held in this set.
        Specified by:
        toArray in interface java.util.Collection<T>
        Specified by:
        toArray in interface java.util.Set<T>
        Type Parameters:
        E - The type of element for the given array.
        Parameters:
        a - An array into which the elements will be added if there is sufficient space.
        Returns:
        The provided array (with the first null element depicting the end of the set elements if the given array is larger than this set), or a newly-allocated array if the provided array was not large enough.

      • hashCode

        public int hashCode()
        Retrieves a hash code for this set.
        Specified by:
        hashCode in interface java.util.Collection<T>
        Specified by:
        hashCode in interface java.util.Set<T>
        Overrides:
        hashCode in class java.lang.Object
        Returns:
        A hash code for this set.

      • equals

        public boolean equals​(java.lang.Object o)
        Indicates whether the provided object is equal to this set.
        Specified by:
        equals in interface java.util.Collection<T>
        Specified by:
        equals in interface java.util.Set<T>
        Overrides:
        equals in class java.lang.Object
        Parameters:
        o - The object for which to make the determination.
        Returns:
        true if the provided object is a non-null set with the same elements as this set, or false if not.

      • toString

        public java.lang.String toString()
        Retrieves a string representation of this set.
        Overrides:
        toString in class java.lang.Object
        Returns:
        A string representation of this set.