Package org.apache.commons.collections4.multiset

Class AbstractMapMultiSet<E>

  • Type Parameters:
    E - the type held in the multiset
    All Implemented Interfaces:
    java.lang.Iterable<E>, java.util.Collection<E>, MultiSet<E>
    Direct Known Subclasses:
    HashMultiSet
    public abstract class AbstractMapMultiSet<E>
extends AbstractMultiSet<E>
    Abstract implementation of the MultiSet interface to simplify the creation of subclass implementations.

    Subclasses specify a Map implementation to use as the internal storage. The map will be used to map multiset elements to a number; the number represents the number of occurrences of that element in the multiset.

    Since:
    4.1

    • Nested Class Summary

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      int add​(E object, int occurrences)
      Adds a number of occurrences of the specified object to the MultiSet.
      void clear()
      Clears the multiset by clearing the underlying map.
      boolean contains​(java.lang.Object object)
      Determines if the multiset contains the given element by checking if the underlying map contains the element as a key.
      boolean equals​(java.lang.Object object)
      Compares this MultiSet to another object.
      int getCount​(java.lang.Object object)
      Returns the number of occurrence of the given element in this multiset by looking up its count in the underlying map.
      int hashCode()
      Gets a hash code for the MultiSet compatible with the definition of equals.
      boolean isEmpty()
      Returns true if the underlying map is empty.
      java.util.Iterator<E> iterator()
      Gets an iterator over the multiset elements.
      int remove​(java.lang.Object object, int occurrences)
      Removes a number of occurrences of the specified object from the MultiSet.
      int size()
      Returns the number of elements in this multiset.
      java.lang.Object[] toArray()
      Returns an array of all of this multiset's elements.
      <T> T[] toArray​(T[] array)
      Returns an array of all of this multiset's elements.

      • Methods inherited from class java.util.AbstractCollection

        addAll, containsAll, retainAll

      • Methods inherited from class java.lang.Object

        getClass, notify, notifyAll, wait, wait, wait

      • Methods inherited from interface java.util.Collection

        addAll, parallelStream, removeIf, spliterator, stream, toArray

      • Methods inherited from interface java.lang.Iterable

        forEach

    • Method Detail

      • size

        public int size()
        Returns the number of elements in this multiset.
        Specified by:
        size in interface java.util.Collection<E>
        Specified by:
        size in interface MultiSet<E>
        Overrides:
        size in class AbstractMultiSet<E>
        Returns:
        current size of the multiset

      • isEmpty

        public boolean isEmpty()
        Returns true if the underlying map is empty.
        Specified by:
        isEmpty in interface java.util.Collection<E>
        Overrides:
        isEmpty in class java.util.AbstractCollection<E>
        Returns:
        true if multiset is empty

      • getCount

        public int getCount​(java.lang.Object object)
        Returns the number of occurrence of the given element in this multiset by looking up its count in the underlying map.
        Specified by:
        getCount in interface MultiSet<E>
        Overrides:
        getCount in class AbstractMultiSet<E>
        Parameters:
        object - the object to search for
        Returns:
        the number of occurrences of the object, zero if not found

      • contains

        public boolean contains​(java.lang.Object object)
        Determines if the multiset contains the given element by checking if the underlying map contains the element as a key.
        Specified by:
        contains in interface java.util.Collection<E>
        Overrides:
        contains in class AbstractMultiSet<E>
        Parameters:
        object - the object to search for
        Returns:
        true if the multiset contains the given element

      • iterator

        public java.util.Iterator<E> iterator()
        Gets an iterator over the multiset elements. Elements present in the MultiSet more than once will be returned repeatedly.
        Specified by:
        iterator in interface java.util.Collection<E>
        Specified by:
        iterator in interface java.lang.Iterable<E>
        Specified by:
        iterator in interface MultiSet<E>
        Overrides:
        iterator in class AbstractMultiSet<E>
        Returns:
        the iterator

      • add

        public int add​(E object,
               int occurrences)
        Description copied from interface: MultiSet
        Adds a number of occurrences of the specified object to the MultiSet.

        If the object is already in the MultiSet.uniqueSet() then increment its count as reported by MultiSet.getCount(Object). Otherwise add it to the MultiSet.uniqueSet() and report its count as occurrences.

        Specified by:
        add in interface MultiSet<E>
        Overrides:
        add in class AbstractMultiSet<E>
        Parameters:
        object - the object to add
        occurrences - the number of occurrences to add, may be zero, in which case no change is made to the multiset
        Returns:
        the number of occurrences of the object in the multiset before this operation; possibly zero

      • clear

        public void clear()
        Clears the multiset by clearing the underlying map.
        Specified by:
        clear in interface java.util.Collection<E>
        Overrides:
        clear in class AbstractMultiSet<E>

      • remove

        public int remove​(java.lang.Object object,
                  int occurrences)
        Description copied from interface: MultiSet
        Removes a number of occurrences of the specified object from the MultiSet.

        If the number of occurrences to remove is greater than the actual number of occurrences in the multiset, the object will be removed from the multiset.

        Specified by:
        remove in interface MultiSet<E>
        Overrides:
        remove in class AbstractMultiSet<E>
        Parameters:
        object - the object to remove
        occurrences - the number of occurrences to remove, may be zero, in which case no change is made to the multiset
        Returns:
        the number of occurrences of the object in the multiset before the operation; possibly zero

      • toArray

        public java.lang.Object[] toArray()
        Returns an array of all of this multiset's elements.
        Specified by:
        toArray in interface java.util.Collection<E>
        Overrides:
        toArray in class java.util.AbstractCollection<E>
        Returns:
        an array of all of this multiset's elements

      • toArray

        public <T> T[] toArray​(T[] array)
        Returns an array of all of this multiset's elements. If the input array has more elements than are in the multiset, trailing elements will be set to null.
        Specified by:
        toArray in interface java.util.Collection<E>
        Overrides:
        toArray in class java.util.AbstractCollection<E>
        Type Parameters:
        T - the type of the array elements
        Parameters:
        array - the array to populate
        Returns:
        an array of all of this multiset's elements
        Throws:
        java.lang.ArrayStoreException - if the runtime type of the specified array is not a supertype of the runtime type of the elements in this list
        java.lang.NullPointerException - if the specified array is null

      • equals

        public boolean equals​(java.lang.Object object)
        Description copied from interface: MultiSet
        Compares this MultiSet to another object.

        This MultiSet equals another object if it is also a MultiSet that contains the same number of occurrences of the same elements.

        Specified by:
        equals in interface java.util.Collection<E>
        Specified by:
        equals in interface MultiSet<E>
        Overrides:
        equals in class AbstractMultiSet<E>
        Parameters:
        object - the object to compare to
        Returns:
        true if equal

      • hashCode

        public int hashCode()
        Description copied from interface: MultiSet
        Gets a hash code for the MultiSet compatible with the definition of equals. The hash code is defined as the sum total of a hash code for each element. The per element hash code is defined as (e==null ? 0 : e.hashCode()) ^ noOccurances).
        Specified by:
        hashCode in interface java.util.Collection<E>
        Specified by:
        hashCode in interface MultiSet<E>
        Overrides:
        hashCode in class AbstractMultiSet<E>
        Returns:
        the hash code of the MultiSet