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 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
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 *      http://www.apache.org/licenses/LICENSE-2.0
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package org.apache.commons.collections4.multiset;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.Collection;
import java.util.HashMap;

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.

Type parameters:
  • <E> – the type held in the multiset
Since:4.1
/** * Implements {@code MultiSet}, using a {@link HashMap} to provide the * data storage. This is the standard implementation of a multiset. * <p> * A {@code 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. * * @param <E> the type held in the multiset * @since 4.1 */
public class HashMultiSet<E> extends AbstractMapMultiSet<E> implements Serializable {
Serial version lock
/** Serial version lock */
private static final long serialVersionUID = 20150610L;
Constructs an empty HashMultiSet.
/** * Constructs an empty {@link HashMultiSet}. */
public HashMultiSet() { super(new HashMap<E, MutableInteger>()); }
Constructs a multiset containing all the members of the given collection.
Params:
  • coll – a collection to copy into this multiset
/** * Constructs a multiset containing all the members of the given collection. * * @param coll a collection to copy into this multiset */
public HashMultiSet(final Collection<? extends E> coll) { this(); addAll(coll); } //-----------------------------------------------------------------------
Write the multiset out using a custom routine.
Params:
  • out – the output stream
Throws:
  • IOException – if an error occurs while writing to the stream
/** * Write the multiset out using a custom routine. * * @param out the output stream * @throws IOException if an error occurs while writing to the stream */
private void writeObject(final ObjectOutputStream out) throws IOException { out.defaultWriteObject(); super.doWriteObject(out); }
Read the multiset in using a custom routine.
Params:
  • in – the input stream
Throws:
/** * Read the multiset in using a custom routine. * * @param in the input stream * @throws IOException if an error occurs while reading from the stream * @throws ClassNotFoundException if an object read from the stream can not be loaded */
private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException { in.defaultReadObject(); setMap(new HashMap<E, MutableInteger>()); super.doReadObject(in); } }