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

This class provides 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 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.

Authors:
Chuck Burdick
Michael A. Smith
Since:
2.0

Constructor Summary

DefaultMapBag()
Constructor.

Method Summary

boolean
add(Object o)
Adds a new element to the bag by incrementing its count in the underlying map.
boolean
add(Object o, int i)
Adds a new element to the bag by incrementing its count in the map.
boolean
addAll(Collection c)
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 o)
Determines if the bag contains the given element by checking if the underlying map contains the element as a key.
boolean
containsAll(Collection c)
boolean
containsAll(Bag other)
Returns true if the bag contains all elements in the given collection, respecting cardinality.
boolean
equals(Object o)
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 o)
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 o)
boolean
remove(Object o, int i)
boolean
removeAll(Collection c)
boolean
retainAll(Collection c)
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 m)
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[] a)
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()

Method Details

add

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

add

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

addAll

public boolean addAll(Collection c)
Invokes add(Object) for each element in the given collection.
See Also:
Bag.addAll(Collection)

calcTotalSize

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

clear

public void clear()
Clears the bag by clearing the underlying map.

contains

public boolean contains(Object o)
Determines if the bag contains the given element by checking if the underlying map contains the element as a key.
Returns:
true if the bag contains the given element

containsAll

public boolean containsAll(Collection c)
Specified by:
containsAll in interface Bag

containsAll

public boolean containsAll(Bag other)
Returns true if the bag contains all elements in the given collection, respecting cardinality.

equals

public boolean equals(Object o)
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:
o - the object to test for equality
Returns:
true if that object equals this bag

getCount

public int getCount(Object o)
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

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 o)
Specified by:
remove in interface Bag

remove

public boolean remove(Object o,
                      int i)
Specified by:
remove in interface Bag

removeAll

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

retainAll

public boolean retainAll(Collection c)
Remove any members of the bag that are not in the given bag, respecting cardinality.
Specified by:
retainAll in interface Bag
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.
Returns:
true if this call changed the collection

setMap

protected void setMap(Map m)
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[] a)
Returns an array of all of this bag's elements.
Parameters:
a - 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

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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