org.apache.commons.collections.bag
Class AbstractMapBag

java.lang.Object
  extended by org.apache.commons.collections.bag.AbstractMapBag
All Implemented Interfaces:
java.lang.Iterable, java.util.Collection, Bag
Direct Known 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)
Version:
$Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
Author:
Chuck Burdick, Michael A. Smith, Stephen Colebourne, Janek Bogucki, Steve Clark

Nested Class Summary
protected static class AbstractMapBag.MutableInteger
          Mutable integer class for storing the data.
 
Constructor Summary
protected AbstractMapBag()
          Constructor needed for subclass serialisation.
protected AbstractMapBag(java.util.Map map)
          Constructor that assigns the specified Map as the backing store.
 
Method Summary
 boolean add(java.lang.Object object)
          Adds a new element to the bag, incrementing its count in the underlying map.
 boolean add(java.lang.Object object, int nCopies)
          Adds a new element to the bag, incrementing its count in the map.
 boolean addAll(java.util.Collection coll)
          Invokes add(Object) for each element in the given collection.
 void clear()
          Clears the bag by clearing the underlying map.
 boolean contains(java.lang.Object object)
          Determines if the bag contains the given element by checking if the underlying map contains the element as a key.
 boolean containsAll(java.util.Collection coll)
          Determines if the bag contains the given elements.
protected  void doReadObject(java.util.Map map, java.io.ObjectInputStream in)
          Read the map in using a custom routine.
protected  void doWriteObject(java.io.ObjectOutputStream out)
          Write the map out using a custom routine.
 boolean equals(java.lang.Object object)
          Compares this Bag to another.
 int getCount(java.lang.Object object)
          Returns the number of occurrence of the given element in this bag by looking up its count in the underlying map.
protected  java.util.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.
 java.util.Iterator iterator()
          Gets an iterator over the bag elements.
 boolean remove(java.lang.Object object)
          Removes all copies of the specified object from the bag.
 boolean remove(java.lang.Object object, int nCopies)
          Removes a specified number of copies of an object from the bag.
 boolean removeAll(java.util.Collection coll)
          Removes objects from the bag according to their count in the specified collection.
 boolean retainAll(java.util.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.
 java.lang.Object[] toArray()
          Returns an array of all of this bag's elements.
 java.lang.Object[] toArray(java.lang.Object[] array)
          Returns an array of all of this bag's elements.
 java.lang.String toString()
          Implement a toString() method suitable for debugging.
 java.util.Set uniqueSet()
          Returns an unmodifiable view of the underlying map's key set.
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
 

Constructor Detail

AbstractMapBag

protected AbstractMapBag()
Constructor needed for subclass serialisation.


AbstractMapBag

protected AbstractMapBag(java.util.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

getMap

protected java.util.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

size

public int size()
Returns the number of elements in this bag.

Specified by:
size in interface java.util.Collection
Specified by:
size in interface Bag
Returns:
current size of the bag

isEmpty

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

Specified by:
isEmpty in interface java.util.Collection
Returns:
true if bag is empty

getCount

public int getCount(java.lang.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

contains

public boolean contains(java.lang.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 java.util.Collection
Parameters:
object - the object to search for
Returns:
true if the bag contains the given element

containsAll

public boolean containsAll(java.util.Collection coll)
Determines if the bag contains the given elements.

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

iterator

public java.util.Iterator 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 java.lang.Iterable
Specified by:
iterator in interface java.util.Collection
Specified by:
iterator in interface Bag
Returns:
the iterator

add

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

Specified by:
add in interface java.util.Collection
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(java.lang.Object object,
                   int nCopies)
Adds a new element to the bag, 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(java.util.Collection coll)
Invokes add(Object) for each element in the given collection.

Specified by:
addAll in interface java.util.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.

Specified by:
clear in interface java.util.Collection

remove

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

Specified by:
remove in interface java.util.Collection
Specified by:
remove in interface Bag
Parameters:
object - the object to remove
Returns:
true if the bag changed

remove

public boolean remove(java.lang.Object object,
                      int nCopies)
Removes a specified number of copies of an object from the bag.

Specified by:
remove in interface Bag
Parameters:
object - the object to remove
nCopies - the number of copies to remove
Returns:
true if the bag changed

removeAll

public boolean removeAll(java.util.Collection coll)
Removes objects from the bag according to their count in the specified collection.

Specified by:
removeAll in interface java.util.Collection
Specified by:
removeAll in interface Bag
Parameters:
coll - the collection to use
Returns:
true if the bag changed

retainAll

public boolean retainAll(java.util.Collection coll)
Remove any members of the bag that are not in the given bag, respecting cardinality.

Specified by:
retainAll in interface java.util.Collection
Specified by:
retainAll in interface Bag
Parameters:
coll - the collection to retain
Returns:
true if this call changed the collection

toArray

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

Specified by:
toArray in interface java.util.Collection
Returns:
an array of all of this bag's elements

toArray

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

Specified by:
toArray in interface java.util.Collection
Parameters:
array - the array to populate
Returns:
an array of all of this bag's elements

uniqueSet

public java.util.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

doWriteObject

protected void doWriteObject(java.io.ObjectOutputStream out)
                      throws java.io.IOException
Write the map out using a custom routine.

Parameters:
out - the output stream
Throws:
java.io.IOException

doReadObject

protected void doReadObject(java.util.Map map,
                            java.io.ObjectInputStream in)
                     throws java.io.IOException,
                            java.lang.ClassNotFoundException
Read the map in using a custom routine.

Parameters:
map - the map to use
in - the input stream
Throws:
java.io.IOException
java.lang.ClassNotFoundException

equals

public boolean equals(java.lang.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 java.util.Collection
Overrides:
equals in class java.lang.Object
Parameters:
object - the Bag to compare to
Returns:
true if equal

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.

Specified by:
hashCode in interface java.util.Collection
Overrides:
hashCode in class java.lang.Object
Returns:
the hash code of the Bag

toString

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

Overrides:
toString in class java.lang.Object
Returns:
a debugging toString


Copyright 2001-2008 The Apache Software Foundation. All Rights Reserved.