Package org.apache.commons.collections4.bag

Class AbstractMapBag<E>

java.lang.Object
org.apache.commons.collections4.bag.AbstractMapBag<E>
Type Parameters:
E - the type of elements in this bag
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)

  • Constructor Details

    • 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

    • AbstractMapBag

      protected AbstractMapBag(Map<E,AbstractMapBag.MutableInteger> map, Iterable<? extends E> iterable)
      Constructs a new instance that assigns the specified Map as the backing store. The map must be empty and non-null. The bag is filled from the iterable elements.
      Parameters:
      map - the map to assign.
      iterable - The bag is filled from these iterable elements.

  • Method Details

    • 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 Bag<E>
      Specified by:
      add in interface Collection<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.
      Specified by:
      clear in interface Collection<E>

    • 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 Bag<E>
      Specified by:
      containsAll in interface Collection<E>
      Parameters:
      coll - the collection to check against
      Returns:
      true if the Bag contains all the collection

    • doReadObject

      protected void doReadObject(Map<E,AbstractMapBag.MutableInteger> map, ObjectInputStream in) throws IOException, ClassNotFoundException
      Read the map in using a custom routine.
      Parameters:
      map - the map to use
      in - the input stream
      Throws:
      IOException - any of the usual I/O related exceptions
      ClassNotFoundException - if the stream contains an object which class cannot be loaded
      ClassCastException - if the stream does not contain the correct objects

    • 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

    • 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

    • 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

    • 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()) ^ noOccurrences). 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

    • 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

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

    • remove

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

    • size

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

    • 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

    • toString

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

    • 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