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org.apache.commons.collections.bag

Class AbstractMapBag

java.lang.Object
|
+--org.apache.commons.collections.bag.AbstractMapBag

All Implemented Interfaces:
Bag

Known Direct 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)
Authors:
Chuck Burdick
Michael A. Smith
Stephen Colebourne
Janek Bogucki

Constructor Summary

AbstractMapBag()

Constructor needed for subclass serialisation.

AbstractMapBag(Map map)

Constructor that assigns the specified Map as the backing store.

Method Summary

boolean

add(Object object)

Adds a new element to the bag, incrementing its count in the underlying map.

boolean

add(Object object, int nCopies)

Adds a new element to the bag, incrementing its count in the map.

boolean

addAll(Collection 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.

void

doReadObject(Map map, ObjectInputStream in)

Read the map in using a custom routine.

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.

Map

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

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.

Object[]

toArray(Object[] array)

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

String

toString()

Implement a toString() method suitable for debugging.

Set

uniqueSet()

Returns an unmodifiable view of the underlying map's key set.

Constructor Details

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 Details

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

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

addAll

public boolean addAll(Collection coll)

Invokes add(Object) 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
in

doWriteObject

protected void doWriteObject(ObjectOutputStream out)

Write the map out using a custom routine.

Parameters:
out

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.


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, 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

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

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