org.apache.commons.collections4.bag

Class AbstractMapBag<E>

  • All Implemented Interfaces:
    Iterable<E>, Collection<E>, Bag<E>
    Direct Known Subclasses:
    HashBag, TreeBag 

    public abstract class AbstractMapBag<E>
extends Object
implements Bag<E>
    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:
    3.0 (previously DefaultMapBag v2.0)

    • Nested Class Summary

      Nested Classes

      Modifier and Type Class and Description
      protected static class  AbstractMapBag.MutableInteger
      Mutable integer class for storing the data.

    • Method Summary

      Modifier and Type Method and Description
      boolean add(E object)
      Adds a new element to the bag, incrementing its count in the underlying map.
      boolean add(E object, int nCopies)
      Adds a new element to the bag, incrementing its count in the map.
      boolean addAll(Collection<? extends E> coll)
      Invokes add(Object) for each element in the given collection.
      void clear()
      Clears the bag by clearing the underlying map.
      boolean contains(Object object)
      Determines if the bag contains the given element by checking if the underlying map contains the element as a key.
      boolean containsAll(Collection<?> coll)
      Determines if the bag contains the given elements.
      protected void doReadObject(Map<E,AbstractMapBag.MutableInteger> map, ObjectInputStream in)
      Read the map in using a custom routine.
      protected void doWriteObject(ObjectOutputStream out)
      Write the map out using a custom routine.
      boolean equals(Object object)
      Compares this Bag to another.
      int getCount(Object object)
      Returns the number of occurrence of the given element in this bag by looking up its count in the underlying map.
      protected Map<E,AbstractMapBag.MutableInteger> getMap()
      Utility method for implementations to access the map that backs this bag.
      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.
      Iterator<E> iterator()
      Gets an iterator over the bag elements.
      boolean remove(Object object)
      Removes all copies of the specified object from the bag.
      boolean remove(Object object, int nCopies)
      Removes a specified number of copies of an object from the bag.
      boolean removeAll(Collection<?> coll)
      Removes objects from the bag according to their count in the specified collection.
      boolean retainAll(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.
      Object[] toArray()
      Returns an array of all of this bag's elements.
      <T> T[] toArray(T[] array)
      Returns an array of all of this bag's elements.
      String toString()
      Implement a toString() method suitable for debugging.
      Set<E> uniqueSet()
      Returns an unmodifiable view of the underlying map's key set.

    • Constructor Detail

      • AbstractMapBag

        protected AbstractMapBag()
        Constructor needed for subclass serialisation.

      • AbstractMapBag

        protected AbstractMapBag(Map<E,AbstractMapBag.MutableInteger> map)
        Constructor that assigns the specified Map as the backing store. The map must be empty and non-null.
        Parameters:
        map - the map to assign

    • Method Detail

      • getMap

        protected Map<E,AbstractMapBag.MutableInteger> getMap()
        Utility method for implementations to access the map that backs this bag. Not intended for interactive use outside of subclasses.
        Returns:
        the map being used by the Bag

      • size

        public int size()
        Returns the number of elements in this bag.
        Specified by:
        size in interface  Collection<E>
        Specified by:
        size in interface  Bag<E>
        Returns:
        current size of the bag

      • isEmpty

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

      • getCount

        public int getCount(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<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 bag contains the given element by checking if the underlying map contains the element as a key.
        Specified by:
        contains in interface  Collection<E>
        Parameters:
        object - the object to search for
        Returns:
        true if the bag contains the given element

      • containsAll

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

      • iterator

        public Iterator<E> 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  Iterable<E>
        Specified by:
        iterator in interface  Collection<E>
        Specified by:
        iterator in interface  Bag<E>
        Returns:
        the iterator

      • add

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

      • add

        public boolean add(E object,
                   int nCopies)
        Adds a new element to the bag, incrementing its count in the map.
        Specified by:
        add in interface  Bag<E>
        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(Collection<? extends E> coll)
        Invokes add(Object) for each element in the given collection.
        Specified by:
        addAll in interface  Collection<E>
        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.

      • remove

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

      • remove

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

      • removeAll

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

      • retainAll

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

      • toArray

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

      • toArray

        public <T> T[] toArray(T[] array)
        Returns an array of all of this bag's elements. If the input array has more elements than are in the bag, trailing elements will be set to null.
        Specified by:
        toArray in interface  Collection<E>
        Type Parameters:
        T - the type of the array elements
        Parameters:
        array - the array to populate
        Returns:
        an array of all of this bag'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

      • uniqueSet

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

      • doWriteObject

        protected void doWriteObject(ObjectOutputStream out)
                      throws IOException
        Write the map out using a custom routine.
        Parameters:
        out - the output stream
        Throws:
        IOException - any of the usual I/O related exceptions

      • equals

        public boolean equals(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  Collection<E>
        Overrides:
        equals in class  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  Collection<E>
        Overrides:
        hashCode in class  Object
        Returns:
        the hash code of the Bag

      • toString

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