Package org.apache.commons.collections.bag

Class AbstractMapBag

  • All Implemented Interfaces:
    java.lang.Iterable, java.util.Collection, Bag
    Direct Known Subclasses:
    HashBag, TreeBag
    public abstract class AbstractMapBag
extends java.lang.Object
implements Bag
    Abstract implementation of the Bag 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 bag elements to a number; the number represents the number of occurrences of that element in the bag.

    Since:
    Commons Collections 3.0 (previously DefaultMapBag v2.0)

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      boolean add​(java.lang.Object object)
      Adds a new element to the bag, incrementing its count in the underlying map.
      boolean add​(java.lang.Object object, int nCopies)
      Adds a new element to the bag, incrementing its count in the map.
      boolean addAll​(java.util.Collection coll)
      Invokes add(Object) for each element in the given collection.
      void clear()
      Clears the bag by clearing the underlying map.
      boolean contains​(java.lang.Object object)
      Determines if the bag contains the given element by checking if the underlying map contains the element as a key.
      boolean containsAll​(java.util.Collection coll)
      Determines if the bag contains the given elements.
      boolean equals​(java.lang.Object object)
      Compares this Bag to another.
      int getCount​(java.lang.Object object)
      Returns the number of occurrence of the given element in this bag by looking up its count in the underlying map.
      int hashCode()
      Gets a hash code for the Bag compatible with the definition of equals.
      boolean isEmpty()
      Returns true if the underlying map is empty.
      java.util.Iterator iterator()
      Gets an iterator over the bag elements.
      boolean remove​(java.lang.Object object)
      Removes all copies of the specified object from the bag.
      boolean remove​(java.lang.Object object, int nCopies)
      Removes a specified number of copies of an object from the bag.
      boolean removeAll​(java.util.Collection coll)
      Removes objects from the bag according to their count in the specified collection.
      boolean retainAll​(java.util.Collection coll)
      Remove any members of the bag that are not in the given bag, respecting cardinality.
      int size()
      Returns the number of elements in this bag.
      java.lang.Object[] toArray()
      Returns an array of all of this bag's elements.
      java.lang.Object[] toArray​(java.lang.Object[] array)
      Returns an array of all of this bag's elements.
      java.lang.String toString()
      Implement a toString() method suitable for debugging.
      java.util.Set uniqueSet()
      Returns an unmodifiable view of the underlying map's key set.

      • Methods inherited from class java.lang.Object

        getClass, notify, notifyAll, wait, wait, wait

      • Methods inherited from interface java.util.Collection

        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 bag.
        Specified by:
        size in interface Bag
        Specified by:
        size in interface java.util.Collection
        Returns:
        current size of the bag

      • isEmpty

        public boolean isEmpty()
        Returns true if the underlying map is empty.
        Specified by:
        isEmpty in interface java.util.Collection
        Returns:
        true if bag is empty

      • getCount

        public int getCount​(java.lang.Object object)
        Returns the number of occurrence of the given element in this bag by looking up its count in the underlying map.
        Specified by:
        getCount in interface Bag
        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 bag contains the given element by checking if the underlying map contains the element as a key.
        Specified by:
        contains in interface java.util.Collection
        Parameters:
        object - the object to search for
        Returns:
        true if the bag contains the given element

      • containsAll

        public boolean containsAll​(java.util.Collection coll)
        Determines if the bag contains the given elements.
        Specified by:
        containsAll in interface Bag
        Specified by:
        containsAll in interface java.util.Collection
        Parameters:
        coll - the collection to check against
        Returns:
        true if the Bag contains all the collection

      • iterator

        public java.util.Iterator iterator()
        Gets an iterator over the bag elements. Elements present in the Bag more than once will be returned repeatedly.
        Specified by:
        iterator in interface Bag
        Specified by:
        iterator in interface java.util.Collection
        Specified by:
        iterator in interface java.lang.Iterable
        Returns:
        the iterator

      • add

        public boolean add​(java.lang.Object object)
        Adds a new element to the bag, incrementing its count in the underlying map.
        Specified by:
        add in interface Bag
        Specified by:
        add in interface java.util.Collection
        Parameters:
        object - the object to add
        Returns:
        true if the object was not already in the uniqueSet

      • add

        public boolean add​(java.lang.Object object,
                   int nCopies)
        Adds a new element to the bag, incrementing its count in the map.
        Specified by:
        add in interface Bag
        Parameters:
        object - the object to search for
        nCopies - the number of copies to add
        Returns:
        true if the object was not already in the uniqueSet

      • addAll

        public boolean addAll​(java.util.Collection coll)
        Invokes add(Object) for each element in the given collection.
        Specified by:
        addAll in interface java.util.Collection
        Parameters:
        coll - the collection to add
        Returns:
        true if this call changed the bag

      • clear

        public void clear()
        Clears the bag by clearing the underlying map.
        Specified by:
        clear in interface java.util.Collection

      • remove

        public boolean remove​(java.lang.Object object)
        Removes all copies of the specified object from the bag.
        Specified by:
        remove in interface Bag
        Specified by:
        remove in interface java.util.Collection
        Parameters:
        object - the object to remove
        Returns:
        true if the bag changed

      • remove

        public boolean remove​(java.lang.Object object,
                      int nCopies)
        Removes a specified number of copies of an object from the bag.
        Specified by:
        remove in interface Bag
        Parameters:
        object - the object to remove
        nCopies - the number of copies to remove
        Returns:
        true if the bag changed

      • removeAll

        public boolean removeAll​(java.util.Collection coll)
        Removes objects from the bag according to their count in the specified collection.
        Specified by:
        removeAll in interface Bag
        Specified by:
        removeAll in interface java.util.Collection
        Parameters:
        coll - the collection to use
        Returns:
        true if the bag changed

      • retainAll

        public boolean retainAll​(java.util.Collection coll)
        Remove any members of the bag that are not in the given bag, respecting cardinality.
        Specified by:
        retainAll in interface Bag
        Specified by:
        retainAll in interface java.util.Collection
        Parameters:
        coll - the collection to retain
        Returns:
        true if this call changed the collection

      • toArray

        public java.lang.Object[] toArray()
        Returns an array of all of this bag's elements.
        Specified by:
        toArray in interface java.util.Collection
        Returns:
        an array of all of this bag's elements

      • toArray

        public java.lang.Object[] toArray​(java.lang.Object[] array)
        Returns an array of all of this bag's elements.
        Specified by:
        toArray in interface java.util.Collection
        Parameters:
        array - the array to populate
        Returns:
        an array of all of this bag's elements

      • uniqueSet

        public java.util.Set uniqueSet()
        Returns an unmodifiable view of the underlying map's key set.
        Specified by:
        uniqueSet in interface Bag
        Returns:
        the set of unique elements in this bag

      • equals

        public boolean equals​(java.lang.Object object)
        Compares this Bag to another. This Bag equals another Bag if it contains the same number of occurrences of the same elements.
        Specified by:
        equals in interface java.util.Collection
        Overrides:
        equals in class java.lang.Object
        Parameters:
        object - the Bag to compare to
        Returns:
        true if equal

      • hashCode

        public int hashCode()
        Gets a hash code for the Bag 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). This hash code is compatible with the Set interface.
        Specified by:
        hashCode in interface java.util.Collection
        Overrides:
        hashCode in class java.lang.Object
        Returns:
        the hash code of the Bag

      • toString

        public java.lang.String toString()
        Implement a toString() method suitable for debugging.
        Overrides:
        toString in class java.lang.Object
        Returns:
        a debugging toString