Package org.apache.commons.collections4.multiset

Class AbstractMapMultiSet<E>

java.lang.Object

java.util.AbstractCollection<E>

org.apache.commons.collections4.multiset.AbstractMultiSet<E>

org.apache.commons.collections4.multiset.AbstractMapMultiSet<E>

Type Parameters:

E - the type held in the multiset

All Implemented Interfaces:

Iterable<E>, Collection<E>, MultiSet<E>

Direct Known Subclasses:

HashMultiSet

public abstract class AbstractMapMultiSet<E>
extends AbstractMultiSet<E>

Abstract implementation of the MultiSet 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 multiset elements to a number; the number represents the number of occurrences of that element in the multiset.

Since:

4.1

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
protected static class	AbstractMapMultiSet.EntrySetIterator<E>	Inner class EntrySetIterator.
protected static class	AbstractMapMultiSet.MultiSetEntry<E>	Inner class MultiSetEntry.
protected static class	AbstractMapMultiSet.MutableInteger	Mutable integer class for storing the data.
protected static class	AbstractMapMultiSet.UniqueSetIterator<E>	Inner class UniqueSetIterator.

Nested classes/interfaces inherited from class org.apache.commons.collections4.multiset.AbstractMultiSet

AbstractMultiSet.AbstractEntry<E>, AbstractMultiSet.EntrySet<E>, AbstractMultiSet.UniqueSet<E>

Nested classes/interfaces inherited from interface org.apache.commons.collections4.MultiSet

MultiSet.Entry<E>

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	AbstractMapMultiSet()	Constructor needed for subclass serialisation.
protected	AbstractMapMultiSet(Map<E,AbstractMapMultiSet.MutableInteger> map)	Constructor that assigns the specified Map as the backing store.

Method Summary

Modifier and Type	Method	Description
int	add(E object, int occurrences)	Adds a number of occurrences of the specified object to the MultiSet.
void	clear()	Clears the multiset by clearing the underlying map.
boolean	contains(Object object)	Determines if the multiset contains the given element by checking if the underlying map contains the element as a key.
protected Iterator<MultiSet.Entry<E>>	createEntrySetIterator()	Creates an entry set iterator.
protected Iterator<E>	createUniqueSetIterator()	Creates a unique set iterator.
protected void	doReadObject(ObjectInputStream in)	Read the multiset in using a custom routine.
protected void	doWriteObject(ObjectOutputStream out)	Write the multiset out using a custom routine.
boolean	equals(Object object)	Compares this MultiSet to another object.
int	getCount(Object object)	Returns the number of occurrence of the given element in this multiset by looking up its count in the underlying map.
protected Map<E,AbstractMapMultiSet.MutableInteger>	getMap()	Utility method for implementations to access the map that backs this multiset.
int	hashCode()	Gets a hash code for the MultiSet compatible with the definition of equals.
boolean	isEmpty()	Returns true if the underlying map is empty.
Iterator<E>	iterator()	Gets an iterator over the multiset elements.
int	remove(Object object, int occurrences)	Removes a number of occurrences of the specified object from the MultiSet.
protected void	setMap(Map<E,AbstractMapMultiSet.MutableInteger> map)	Sets the map being wrapped.
int	size()	Returns the number of elements in this multiset.
Object[]	toArray()	Returns an array of all of this multiset's elements.
<T> T[]	toArray(T[] array)	Returns an array of all of this multiset's elements.
protected int	uniqueElements()	Returns the number of unique elements in this multiset.

Methods inherited from class org.apache.commons.collections4.multiset.AbstractMultiSet

add, createEntrySet, createUniqueSet, entrySet, remove, removeAll, setCount, toString, uniqueSet

Methods inherited from class java.util.AbstractCollection

addAll, containsAll, retainAll

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Collection

addAll, parallelStream, removeIf, spliterator, stream, toArray

Methods inherited from interface java.lang.Iterable

forEach

Methods inherited from interface org.apache.commons.collections4.MultiSet

containsAll, retainAll

Constructor Detail

AbstractMapMultiSet

protected AbstractMapMultiSet()

Constructor needed for subclass serialisation.

AbstractMapMultiSet

protected AbstractMapMultiSet(Map<E,AbstractMapMultiSet.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

Method Detail

getMap

protected Map<E,AbstractMapMultiSet.MutableInteger> getMap()

Utility method for implementations to access the map that backs this multiset. Not intended for interactive use outside of subclasses.

Returns:

the map being used by the MultiSet

setMap

protected void setMap(Map<E,AbstractMapMultiSet.MutableInteger> map)

Sets the map being wrapped.

NOTE: this method should only be used during deserialization

Parameters:

map - the map to wrap

size

public int size()

Returns the number of elements in this multiset.

Specified by:

size in interface Collection<E>

Specified by:

size in interface MultiSet<E>

Overrides:

size in class AbstractMultiSet<E>

Returns:

current size of the multiset

isEmpty

public boolean isEmpty()

Returns true if the underlying map is empty.

Specified by:

isEmpty in interface Collection<E>

Overrides:

isEmpty in class AbstractCollection<E>

Returns:

true if multiset is empty

getCount

public int getCount(Object object)

Returns the number of occurrence of the given element in this multiset by looking up its count in the underlying map.

Specified by:

getCount in interface MultiSet<E>

Overrides:

getCount in class AbstractMultiSet<E>

Parameters:

object - the object to search for

Returns:

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

contains

public boolean contains(Object object)

Determines if the multiset contains the given element by checking if the underlying map contains the element as a key.

Specified by:

contains in interface Collection<E>

Overrides:

contains in class AbstractMultiSet<E>

Parameters:

object - the object to search for

Returns:

true if the multiset contains the given element

iterator

public Iterator<E> iterator()

Gets an iterator over the multiset elements. Elements present in the MultiSet more than once will be returned repeatedly.

Specified by:

iterator in interface Collection<E>

Specified by:

iterator in interface Iterable<E>

Specified by:

iterator in interface MultiSet<E>

Overrides:

iterator in class AbstractMultiSet<E>

Returns:

the iterator

add

public int add(E object,
               int occurrences)

Description copied from interface: MultiSet

Adds a number of occurrences of the specified object to the MultiSet.

If the object is already in the MultiSet.uniqueSet() then increment its count as reported by MultiSet.getCount(Object). Otherwise add it to the MultiSet.uniqueSet() and report its count as occurrences.

Specified by:

add in interface MultiSet<E>

Overrides:

add in class AbstractMultiSet<E>

Parameters:

object - the object to add

occurrences - the number of occurrences to add, may be zero, in which case no change is made to the multiset

Returns:

the number of occurrences of the object in the multiset before this operation; possibly zero

clear

public void clear()

Clears the multiset by clearing the underlying map.

Specified by:

clear in interface Collection<E>

Overrides:

clear in class AbstractMultiSet<E>

remove

public int remove(Object object,
                  int occurrences)

Description copied from interface: MultiSet

Removes a number of occurrences of the specified object from the MultiSet.

If the number of occurrences to remove is greater than the actual number of occurrences in the multiset, the object will be removed from the multiset.

Specified by:

remove in interface MultiSet<E>

Overrides:

remove in class AbstractMultiSet<E>

Parameters:

object - the object to remove

occurrences - the number of occurrences to remove, may be zero, in which case no change is made to the multiset

Returns:

the number of occurrences of the object in the multiset before the operation; possibly zero

createUniqueSetIterator

protected Iterator<E> createUniqueSetIterator()

Description copied from class: AbstractMultiSet

Creates a unique set iterator. Subclasses can override this to return iterators with different properties.

Overrides:

createUniqueSetIterator in class AbstractMultiSet<E>

Returns:

the uniqueSet iterator

uniqueElements

protected int uniqueElements()

Description copied from class: AbstractMultiSet

Returns the number of unique elements in this multiset.

Specified by:

uniqueElements in class AbstractMultiSet<E>

Returns:

the number of unique elements

createEntrySetIterator

protected Iterator<MultiSet.Entry<E>> createEntrySetIterator()

Description copied from class: AbstractMultiSet

Creates an entry set iterator. Subclasses can override this to return iterators with different properties.

Specified by:

createEntrySetIterator in class AbstractMultiSet<E>

Returns:

the entrySet iterator

doWriteObject

protected void doWriteObject(ObjectOutputStream out)
                      throws IOException

Write the multiset out using a custom routine.

Overrides:

doWriteObject in class AbstractMultiSet<E>

Parameters:

out - the output stream

Throws:

IOException - any of the usual I/O related exceptions

doReadObject

protected void doReadObject(ObjectInputStream in)
                     throws IOException,
                            ClassNotFoundException

Read the multiset in using a custom routine.

Overrides:

doReadObject in class AbstractMultiSet<E>

Parameters:

in - the input stream

Throws:

IOException - any of the usual I/O related exceptions

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

ClassCastException - if the stream does not contain the correct objects

toArray

public Object[] toArray()

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

Specified by:

toArray in interface Collection<E>

Overrides:

toArray in class AbstractCollection<E>

Returns:

an array of all of this multiset's elements

toArray

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

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

Specified by:

toArray in interface Collection<E>

Overrides:

toArray in class AbstractCollection<E>

Type Parameters:

T - the type of the array elements

Parameters:

array - the array to populate

Returns:

an array of all of this multiset'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

equals

public boolean equals(Object object)

Description copied from interface: MultiSet

Compares this MultiSet to another object.

This MultiSet equals another object if it is also a MultiSet that contains the same number of occurrences of the same elements.

Specified by:

equals in interface Collection<E>

Specified by:

equals in interface MultiSet<E>

Overrides:

equals in class AbstractMultiSet<E>

Parameters:

object - the object to compare to

Returns:

true if equal

hashCode

public int hashCode()

Description copied from interface: MultiSet

Gets a hash code for the MultiSet 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).

Specified by:

hashCode in interface Collection<E>

Specified by:

hashCode in interface MultiSet<E>

Overrides:

hashCode in class AbstractMultiSet<E>

Returns:

the hash code of the MultiSet