Package org.apache.commons.collections4.multiset

Class AbstractMapMultiSet<E>

java.lang.Object
java.util.AbstractCollection<E>
org.apache.commons.collections4.multiset.AbstractMultiSet<E>
org.apache.commons.collections4.multiset.AbstractMapMultiSet<E>
Type Parameters:
E - the type held in the multiset
All Implemented Interfaces:
Iterable<E>, 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

  • Method Details

    • size

      public int size()
      Returns the number of elements in this multiset.
      Specified by:
      size in interface 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 Collection<E>
      Overrides:
      isEmpty in class AbstractCollection<E>
      Returns:
      true if multiset is empty

    • getCount

      public int getCount(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(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 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 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 Collection<E>
      Specified by:
      iterator in interface 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 Collection<E>
      Overrides:
      clear in class AbstractMultiSet<E>

    • remove

      public int remove(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 Object[] toArray()
      Returns an array of all of this multiset's elements.
      Specified by:
      toArray in interface Collection<E>
      Overrides:
      toArray in class 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 Collection<E>
      Overrides:
      toArray in class 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:
      ArrayStoreException - if the runtime type of the specified array is not a supertype of the runtime type of the elements in this list
      NullPointerException - if the specified array is null

    • equals

      public boolean equals(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 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 Collection<E>
      Specified by:
      hashCode in interface MultiSet<E>
      Overrides:
      hashCode in class AbstractMultiSet<E>
      Returns:
      the hash code of the MultiSet