Package org.apache.commons.collections4.bag

Class AbstractMapBag<E>

java.lang.Object

org.apache.commons.collections4.bag.AbstractMapBag<E>

Type Parameters:

E - the type of elements in this bag

All Implemented Interfaces:

Iterable<E>, Collection<E>, Bag<E>

Direct Known Subclasses:

HashBag, TreeBag

public abstract class AbstractMapBag<E>
extends Object
implements Bag<E>

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:

3.0 (previously DefaultMapBag v2.0)

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
protected static class	AbstractMapBag.MutableInteger	Mutable integer class for storing the data.

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	AbstractMapBag()	Constructor needed for subclass serialisation.
protected	AbstractMapBag(Map<E,AbstractMapBag.MutableInteger> map)	Constructor that assigns the specified Map as the backing store.
protected	AbstractMapBag(Map<E,AbstractMapBag.MutableInteger> map, Iterable<? extends E> iterable)	Constructs a new instance that assigns the specified Map as the backing store.

Method Summary

Modifier and Type	Method	Description
boolean	add(E object)	Adds a new element to the bag, incrementing its count in the underlying map.
boolean	add(E object, int nCopies)	Adds a new element to the bag, incrementing its count in the map.
boolean	addAll(Collection<? extends E> 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.
protected void	doReadObject(Map<E,AbstractMapBag.MutableInteger> map, ObjectInputStream in)	Read the map in using a custom routine.
protected 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.
protected Map<E,AbstractMapBag.MutableInteger>	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<E>	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.
<T> T[]	toArray(T[] array)	Returns an array of all of this bag's elements.
String	toString()	Implement a toString() method suitable for debugging.
Set<E>	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

Methods inherited from interface java.util.Collection

parallelStream, removeIf, spliterator, stream

Methods inherited from interface java.lang.Iterable

forEach

Constructor Details

AbstractMapBag

protected AbstractMapBag()

Constructor needed for subclass serialisation.

AbstractMapBag

protected AbstractMapBag(Map<E,AbstractMapBag.MutableInteger> 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

AbstractMapBag

protected AbstractMapBag(Map<E,AbstractMapBag.MutableInteger> map,
 Iterable<? extends E> iterable)

Constructs a new instance that assigns the specified Map as the backing store. The map must be empty and non-null. The bag is filled from the iterable elements.

Parameters:

map - the map to assign.

iterable - The bag is filled from these iterable elements.

Method Details

add

public boolean add(E object)

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

Specified by:

add in interface Bag<E>

Specified by:

add in interface Collection<E>

Parameters:

object - the object to add

Returns:

true if the object was not already in the uniqueSet

add

public boolean add(E object,
 int nCopies)

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

Specified by:

add in interface Bag<E>

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<? extends E> coll)

Invokes add(Object) for each element in the given collection.

Specified by:

addAll in interface Collection<E>

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 Collection<E>

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.

Specified by:

contains in interface Collection<E>

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<E>

Specified by:

containsAll in interface Collection<E>

Parameters:

coll - the collection to check against

Returns:

true if the Bag contains all the collection

doReadObject

protected void doReadObject(Map<E,AbstractMapBag.MutableInteger> map,
 ObjectInputStream in)
                     throws IOException,
ClassNotFoundException

Read the map in using a custom routine.

Parameters:

map - the map to use

in - the input stream

Throws:

IOException - any of the usual I/O related exceptions

ClassNotFoundException - if the stream contains an object which class cannot be loaded

ClassCastException - if the stream does not contain the correct objects

doWriteObject

protected void doWriteObject(ObjectOutputStream out)
                      throws IOException

Write the map out using a custom routine.

Parameters:

out - the output stream

Throws:

IOException - any of the usual I/O related exceptions

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.

Specified by:

equals in interface Collection<E>

Overrides:

equals in class Object

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.

Specified by:

getCount in interface Bag<E>

Parameters:

object - the object to search for

Returns:

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

getMap

protected Map<E,AbstractMapBag.MutableInteger> 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()) ^ noOccurrences). This hash code is compatible with the Set interface.

Specified by:

hashCode in interface Collection<E>

Overrides:

hashCode in class Object

Returns:

the hash code of the Bag

isEmpty

public boolean isEmpty()

Returns true if the underlying map is empty.

Specified by:

isEmpty in interface Collection<E>

Returns:

true if bag is empty

iterator

public Iterator<E> 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 Bag<E>

Specified by:

iterator in interface Collection<E>

Specified by:

iterator in interface Iterable<E>

Returns:

the iterator

remove

public boolean remove(Object object)

Removes all copies of the specified object from the bag.

Specified by:

remove in interface Bag<E>

Specified by:

remove in interface Collection<E>

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.

Specified by:

remove in interface Bag<E>

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.

Specified by:

removeAll in interface Bag<E>

Specified by:

removeAll in interface Collection<E>

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.

Specified by:

retainAll in interface Bag<E>

Specified by:

retainAll in interface Collection<E>

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.

Specified by:

size in interface Bag<E>

Specified by:

size in interface Collection<E>

Returns:

current size of the bag

toArray

public Object[] toArray()

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

Specified by:

toArray in interface Collection<E>

Returns:

an array of all of this bag's elements

toArray

public <T> T[] toArray(T[] array)

Returns an array of all of this bag's elements. If the input array has more elements than are in the bag, trailing elements will be set to null.

Specified by:

toArray in interface Collection<E>

Type Parameters:

T - the type of the array elements

Parameters:

array - the array to populate

Returns:

an array of all of this bag's elements

Throws:

ArrayStoreException - if the runtime type of the specified array is not a supertype of the runtime type of the elements in this list

NullPointerException - if the specified array is null

toString

public String toString()

Implement a toString() method suitable for debugging.

Overrides:

toString in class Object

Returns:

a debugging toString

uniqueSet

public Set<E> uniqueSet()

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

Specified by:

uniqueSet in interface Bag<E>

Returns:

the set of unique elements in this bag