org.apache.commons.collections

Class DefaultMapBag

Implemented Interfaces:
Bag, Collection
Known Direct Subclasses:
HashBag, TreeBag

public abstract class DefaultMapBag
extends java.lang.Object
implements Bag

A skeletal implementation of the Bag interface to minimize the effort required for target implementations. Subclasses need only to call setMap(Map) in their constructor (or invoke the Map constructor) specifying a map instance that will be used to store the contents of the bag.

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.

Version:
$Revision: 1.17 $ $Date: 2004/02/18 01:15:42 $
Authors:
Chuck Burdick
Michael A. Smith
Stephen Colebourne
Janek Bogucki
Since:
Commons Collections 2.0

Constructor Summary

DefaultMapBag()
No-argument constructor.
DefaultMapBag(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 by incrementing its count in the underlying map.
boolean
add(Object object, int nCopies)
Adds a new element to the bag by incrementing its count in the map.
boolean
addAll(Collection coll)
Invokes add(Object) for each element in the given collection.
protected int
calcTotalSize()
Actually walks the bag to make sure the count is correct and resets the running total
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.
boolean
containsAll(Bag other)
Returns true if the bag contains all elements in the given collection, respecting cardinality.
boolean
equals(Object object)
Returns true if the given object is not null, has the precise type of this bag, and contains the same number of occurrences of all the same elements.
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
getMap()
Utility method for implementations to access the map that backs this bag.
int
hashCode()
Returns the hash code of the underlying map.
boolean
isEmpty()
Returns true if the underlying map is empty.
Iterator
iterator()
boolean
remove(Object object)
boolean
remove(Object object, int nCopies)
boolean
removeAll(Collection coll)
boolean
retainAll(Collection coll)
Remove any members of the bag that are not in the given bag, respecting cardinality.
boolean
retainAll(Bag other)
Remove any members of the bag that are not in the given bag, respecting cardinality.
protected void
setMap(Map map)
Utility method for implementations to set the map that backs this bag.
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

DefaultMapBag

public DefaultMapBag()
No-argument constructor. Subclasses should invoke setMap(Map) in their constructors.

DefaultMapBag

protected DefaultMapBag(Map map)
Constructor that assigns the specified Map as the backing store. The map must be empty.
Parameters:
map - the map to assign

Method Details

add

public boolean add(Object object)
Adds a new element to the bag by incrementing its count in the underlying map.
Specified by:
add in interface Bag
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 by 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(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

calcTotalSize

protected int calcTotalSize()
Actually walks the bag to make sure the count is correct and resets the running total
Returns:
the current total size

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.
Specified by:
containsAll in interface Bag
Parameters:
coll - the collection to check against
Returns:
true if the Bag contains all the collection

containsAll

public boolean containsAll(Bag other)
Returns true if the bag contains all elements in the given collection, respecting cardinality.
Parameters:
other - the bag to check against
Returns:
true if the Bag contains all the collection

equals

public boolean equals(Object object)
Returns true if the given object is not null, has the precise type of this bag, and contains the same number of occurrences of all the same elements.
Parameters:
object - the object to test for equality
Returns:
true if that object equals this bag

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
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()
Returns the hash code of the underlying map.
Returns:
the hash code of the underlying map

isEmpty

public boolean isEmpty()
Returns true if the underlying map is empty.
Returns:
true if there are no elements in this bag

iterator

public Iterator iterator()
Specified by:
iterator in interface Bag

remove

public boolean remove(Object object)
Specified by:
remove in interface Bag

remove

public boolean remove(Object object,
                      int nCopies)
Specified by:
remove in interface Bag

removeAll

public boolean removeAll(Collection coll)
Specified by:
removeAll in interface Bag

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
Parameters:
coll - the collection to retain
Returns:
true if this call changed the collection

retainAll

public boolean retainAll(Bag other)
Remove any members of the bag that are not in the given bag, respecting cardinality.
Parameters:
other - the bag to retain
Returns:
true if this call changed the collection

setMap

protected void setMap(Map map)
Utility method for implementations to set the map that backs this bag. Not intended for interactive use outside of subclasses.

size

public int size()
Returns the number of elements in this bag.
Specified by:
size in interface Bag
Returns:
the number of elements in this 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.
Specified by:
uniqueSet in interface Bag
Returns:
the set of unique elements in this bag

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