HashMultiSet

java.lang.Object
- java.util.AbstractCollection<E>
- - org.apache.commons.collections4.multiset.AbstractMultiSet<E>
  - - org.apache.commons.collections4.multiset.AbstractMapMultiSet<E>
    - - org.apache.commons.collections4.multiset.HashMultiSet<E>

Type Parameters:

E - the type held in the multiset

All Implemented Interfaces:

java.io.Serializable, java.lang.Iterable<E>, java.util.Collection<E>, MultiSet<E>
```
public class HashMultiSet<E>
extends AbstractMapMultiSet<E>
implements java.io.Serializable
```
Implements MultiSet, using a HashMap to provide the data storage. This is the standard implementation of a multiset.
A MultiSet stores each object in the collection together with a count of occurrences. Extra methods on the interface allow multiple copies of an object to be added or removed at once.

Since:

4.1

See Also:

Serialized Form

Nested Class Summary
- Nested classes/interfaces inherited from class org.apache.commons.collections4.multiset.AbstractMapMultiSet
  AbstractMapMultiSet.EntrySetIterator<E>, AbstractMapMultiSet.MultiSetEntry<E>, AbstractMapMultiSet.MutableInteger, AbstractMapMultiSet.UniqueSetIterator<E>
- 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>

Field Summary

Fields
Modifier and Type Field Description

private static long serialVersionUID
Serial version lock

Constructor Summary

Constructors
Constructor	Description
`HashMultiSet()`	Constructs an empty `HashMultiSet`.
`HashMultiSet(java.util.Collection<? extends E> coll)`	Constructs a multiset containing all the members of the given collection.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`private void`	`readObject(java.io.ObjectInputStream in)`	Read the multiset in using a custom routine.
`private void`	`writeObject(java.io.ObjectOutputStream out)`	Write the multiset out using a custom routine.

Methods inherited from class org.apache.commons.collections4.multiset.AbstractMapMultiSet
add, clear, contains, createEntrySetIterator, createUniqueSetIterator, doReadObject, doWriteObject, equals, getCount, getMap, hashCode, isEmpty, iterator, remove, setMap, size, toArray, toArray, uniqueElements

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

- Field Detail
  - serialVersionUID
```
private static final long serialVersionUID
```
    Serial version lock
    
    See Also:
    
    Constant Field Values
- Constructor Detail
  - HashMultiSet
```
public HashMultiSet()
```
    Constructs an empty HashMultiSet.
  - HashMultiSet
```
public HashMultiSet(java.util.Collection<? extends E> coll)
```
    Constructs a multiset containing all the members of the given collection.
    
    Parameters:
    
    coll - a collection to copy into this multiset
- Method Detail
  - writeObject
```
private void writeObject(java.io.ObjectOutputStream out)
                  throws java.io.IOException
```
    Write the multiset out using a custom routine.
    
    Parameters:
    
    out - the output stream
    
    Throws:
    
    java.io.IOException - if an error occurs while writing to the stream
  - readObject
```
private void readObject(java.io.ObjectInputStream in)
                 throws java.io.IOException,
                        java.lang.ClassNotFoundException
```
    Read the multiset in using a custom routine.
    
    Parameters:
    
    in - the input stream
    
    Throws:
    
    java.io.IOException - if an error occurs while reading from the stream
    
    java.lang.ClassNotFoundException - if an object read from the stream can not be loaded