org.apache.commons.collections.bag

Class AbstractMapBag

public abstract class AbstractMapBag extends 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)

Version: $Revision: 219131 $ $Date: 2005-07-15 00:11:12 +0100 (Fri, 15 Jul 2005) $

Author: Chuck Burdick Michael A. Smith Stephen Colebourne Janek Bogucki Steve Clark

Nested Class Summary
protected static classAbstractMapBag.MutableInteger
Mutable integer class for storing the data.
Constructor Summary
protected AbstractMapBag()
Constructor needed for subclass serialisation.
protected AbstractMapBag(Map map)
Constructor that assigns the specified Map as the backing store.
Method Summary
booleanadd(Object object)
Adds a new element to the bag, incrementing its count in the underlying map.
booleanadd(Object object, int nCopies)
Adds a new element to the bag, incrementing its count in the map.
booleanaddAll(Collection coll)
Invokes add for each element in the given collection.
voidclear()
Clears the bag by clearing the underlying map.
booleancontains(Object object)
Determines if the bag contains the given element by checking if the underlying map contains the element as a key.
booleancontainsAll(Collection coll)
Determines if the bag contains the given elements.
protected voiddoReadObject(Map map, ObjectInputStream in)
Read the map in using a custom routine.
protected voiddoWriteObject(ObjectOutputStream out)
Write the map out using a custom routine.
booleanequals(Object object)
Compares this Bag to another.
intgetCount(Object object)
Returns the number of occurrence of the given element in this bag by looking up its count in the underlying map.
protected MapgetMap()
Utility method for implementations to access the map that backs this bag.
inthashCode()
Gets a hash code for the Bag compatible with the definition of equals.
booleanisEmpty()
Returns true if the underlying map is empty.
Iteratoriterator()
Gets an iterator over the bag elements.
booleanremove(Object object)
Removes all copies of the specified object from the bag.
booleanremove(Object object, int nCopies)
Removes a specified number of copies of an object from the bag.
booleanremoveAll(Collection coll)
Removes objects from the bag according to their count in the specified collection.
booleanretainAll(Collection coll)
Remove any members of the bag that are not in the given bag, respecting cardinality.
intsize()
Returns the number of elements in this bag.
Object[]toArray()
Returns an array of all of this bag's elements.
Object[]toArray(Object[] array)
Returns an array of all of this bag's elements.
StringtoString()
Implement a toString() method suitable for debugging.
SetuniqueSet()
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 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

add

public boolean add(Object object)
Adds a new element to the bag, incrementing its count in the underlying map.

Parameters: object the object to add

Returns: true if the object was not already in the uniqueSet

add

public boolean add(Object object, int nCopies)
Adds a new element to the bag, incrementing its count in the map.

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 coll)
Invokes add for each element in the given 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.

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.

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.

Parameters: coll the collection to check against

Returns: true if the Bag contains all the collection

doReadObject

protected void doReadObject(Map map, ObjectInputStream in)
Read the map in using a custom routine.

Parameters: map the map to use in the input stream

Throws: IOException ClassNotFoundException

doWriteObject

protected void doWriteObject(ObjectOutputStream out)
Write the map out using a custom routine.

Parameters: out the output stream

Throws: IOException

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.

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.

Parameters: object the object to search for

Returns: the number of occurrences of the object, zero if not found

getMap

protected Map 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()) ^ noOccurances). This hash code is compatible with the Set interface.

Returns: the hash code of the Bag

isEmpty

public boolean isEmpty()
Returns true if the underlying map is empty.

Returns: true if bag is empty

iterator

public Iterator iterator()
Gets an iterator over the bag elements. Elements present in the Bag more than once will be returned repeatedly.

Returns: the iterator

remove

public boolean remove(Object object)
Removes all copies of the specified object from the bag.

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.

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.

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.

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.

Returns: current size of the bag

toArray

public Object[] toArray()
Returns an array of all of this bag's elements.

Returns: an array of all of this bag's elements

toArray

public Object[] toArray(Object[] array)
Returns an array of all of this bag's elements.

Parameters: array the array to populate

Returns: an array of all of this bag's elements

toString

public String toString()
Implement a toString() method suitable for debugging.

Returns: a debugging toString

uniqueSet

public Set uniqueSet()
Returns an unmodifiable view of the underlying map's key set.

Returns: the set of unique elements in this bag

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