Package org.apache.commons.collections4.multiset

Class PredicatedMultiSet<E>

java.lang.Object
org.apache.commons.collections4.collection.AbstractCollectionDecorator<E>
org.apache.commons.collections4.collection.PredicatedCollection<E>
org.apache.commons.collections4.multiset.PredicatedMultiSet<E>
Type Parameters:
E - the type held in the multiset
All Implemented Interfaces:
Serializable, Iterable<E>, Collection<E>, MultiSet<E>
public class PredicatedMultiSet<E> extends PredicatedCollection<E> implements MultiSet<E>
Decorates another MultiSet to validate that additions match a specified predicate.

This multiset exists to provide validation for the decorated multiset. It is normally created to decorate an empty multiset. If an object cannot be added to the multiset, an IllegalArgumentException is thrown.

One usage would be to ensure that no null entries are added to the multiset. 

 MultiSet<E> set =
      PredicatedMultiSet.predicatedMultiSet(new HashMultiSet<E>(),
                                            NotNullPredicate.notNullPredicate());
Since:
4.1
See Also:

  • Constructor Details

    • PredicatedMultiSet

      protected PredicatedMultiSet(MultiSet<E> multiset, Predicate<? super E> predicate)
      Constructor that wraps (not copies).

      If there are any elements already in the multiset being decorated, they are validated.

      Parameters:
      multiset - the multiset to decorate, must not be null
      predicate - the predicate to use for validation, must not be null
      Throws:
      NullPointerException - if multiset or predicate is null
      IllegalArgumentException - if the multiset contains invalid elements

  • Method Details

    • predicatedMultiSet

      public static <E> PredicatedMultiSet<E> predicatedMultiSet(MultiSet<E> multiset, Predicate<? super E> predicate)
      Factory method to create a predicated (validating) multiset.

      If there are any elements already in the multiset being decorated, they are validated.

      Type Parameters:
      E - the type of the elements in the multiset
      Parameters:
      multiset - the multiset to decorate, must not be null
      predicate - the predicate to use for validation, must not be null
      Returns:
      a new predicated MultiSet
      Throws:
      NullPointerException - if multiset or predicate is null
      IllegalArgumentException - if the multiset contains invalid elements

    • add

      public int add(E object, int count)
      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>
      Parameters:
      object - the object to add
      count - 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

    • decorated

      protected MultiSet<E> decorated()
      Gets the decorated multiset.
      Overrides:
      decorated in class AbstractCollectionDecorator<E>
      Returns:
      the decorated multiset

    • entrySet

      public Set<MultiSet.Entry<E>> entrySet()
      Description copied from interface: MultiSet
      Returns a Set of all entries contained in the MultiSet.

      The returned set is backed by this multiset, so any change to either is immediately reflected in the other.

      Specified by:
      entrySet in interface MultiSet<E>
      Returns:
      the Set of MultiSet entries

    • 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 Object
      Parameters:
      object - the object to compare to
      Returns:
      true if equal

    • getCount

      public int getCount(Object object)
      Description copied from interface: MultiSet
      Returns the number of occurrences of the given object currently in the MultiSet. If the object does not exist in the multiset, return 0.
      Specified by:
      getCount in interface MultiSet<E>
      Parameters:
      object - the object to search for
      Returns:
      the number of occurrences of the object, zero if not found

    • 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()) ^ noOccurrences).
      Specified by:
      hashCode in interface Collection<E>
      Specified by:
      hashCode in interface MultiSet<E>
      Overrides:
      hashCode in class Object
      Returns:
      the hash code of the MultiSet

    • remove

      public int remove(Object object, int count)
      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>
      Parameters:
      object - the object to remove
      count - 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

    • setCount

      public int setCount(E object, int count)
      Description copied from interface: MultiSet
      Sets the number of occurrences of the specified object in the MultiSet to the given count.

      If the provided count is zero, the object will be removed from the MultiSet.uniqueSet().

      Specified by:
      setCount in interface MultiSet<E>
      Parameters:
      object - the object to update
      count - the number of occurrences of the object
      Returns:
      the number of occurrences of the object before this operation, zero if the object was not contained in the multiset

    • uniqueSet

      public Set<E> uniqueSet()
      Description copied from interface: MultiSet
      Returns a Set of unique elements in the MultiSet.

      Uniqueness constraints are the same as those in Set.

      The returned set is backed by this multiset, so any change to either is immediately reflected in the other. Only removal operations are supported, in which case all occurrences of the element are removed from the backing multiset.

      Specified by:
      uniqueSet in interface MultiSet<E>
      Returns:
      the Set of unique MultiSet elements