org.apache.commons.collections4.multiset.AbstractMapMultiSet Maven / Gradle / Ivy
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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* 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
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.collections4.multiset;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.lang.reflect.Array;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.Map;
import org.apache.commons.collections4.MultiSet;
import org.apache.commons.collections4.iterators.AbstractIteratorDecorator;
/**
* Abstract implementation of the {@link 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.
*
* @param the type held in the multiset
* @since 4.1
*/
public abstract class AbstractMapMultiSet extends AbstractMultiSet {
/** The map to use to store the data */
private transient Map map;
/** The current total size of the multiset */
private transient int size;
/** The modification count for fail fast iterators */
private transient int modCount;
/**
* Constructor needed for subclass serialisation.
*/
protected AbstractMapMultiSet() {
super();
}
/**
* Constructor that assigns the specified Map as the backing store. The map
* must be empty and non-null.
*
* @param map the map to assign
*/
protected AbstractMapMultiSet(final Map map) {
super();
this.map = map;
}
/**
* Utility method for implementations to access the map that backs this multiset.
* Not intended for interactive use outside of subclasses.
*
* @return the map being used by the MultiSet
*/
protected Map getMap() {
return map;
}
/**
* Sets the map being wrapped.
*
* NOTE: this method should only be used during deserialization
*
* @param map the map to wrap
*/
protected void setMap(final Map map) {
this.map = map;
}
//-----------------------------------------------------------------------
/**
* Returns the number of elements in this multiset.
*
* @return current size of the multiset
*/
@Override
public int size() {
return size;
}
/**
* Returns true if the underlying map is empty.
*
* @return true if multiset is empty
*/
@Override
public boolean isEmpty() {
return map.isEmpty();
}
/**
* Returns the number of occurrence of the given element in this multiset by
* looking up its count in the underlying map.
*
* @param object the object to search for
* @return the number of occurrences of the object, zero if not found
*/
@Override
public int getCount(final Object object) {
final MutableInteger count = map.get(object);
if (count != null) {
return count.value;
}
return 0;
}
//-----------------------------------------------------------------------
/**
* Determines if the multiset contains the given element by checking if the
* underlying map contains the element as a key.
*
* @param object the object to search for
* @return true if the multiset contains the given element
*/
@Override
public boolean contains(final Object object) {
return map.containsKey(object);
}
//-----------------------------------------------------------------------
/**
* Gets an iterator over the multiset elements. Elements present in the
* MultiSet more than once will be returned repeatedly.
*
* @return the iterator
*/
@Override
public Iterator iterator() {
return new MapBasedMultiSetIterator<>(this);
}
/**
* Inner class iterator for the MultiSet.
*/
private static class MapBasedMultiSetIterator implements Iterator {
private final AbstractMapMultiSet parent;
private final Iterator> entryIterator;
private Map.Entry current;
private int itemCount;
private final int mods;
private boolean canRemove;
/**
* Constructor.
*
* @param parent the parent multiset
*/
public MapBasedMultiSetIterator(final AbstractMapMultiSet parent) {
this.parent = parent;
this.entryIterator = parent.map.entrySet().iterator();
this.current = null;
this.mods = parent.modCount;
this.canRemove = false;
}
/** {@inheritDoc} */
@Override
public boolean hasNext() {
return itemCount > 0 || entryIterator.hasNext();
}
/** {@inheritDoc} */
@Override
public E next() {
if (parent.modCount != mods) {
throw new ConcurrentModificationException();
}
if (itemCount == 0) {
current = entryIterator.next();
itemCount = current.getValue().value;
}
canRemove = true;
itemCount--;
return current.getKey();
}
/** {@inheritDoc} */
@Override
public void remove() {
if (parent.modCount != mods) {
throw new ConcurrentModificationException();
}
if (canRemove == false) {
throw new IllegalStateException();
}
final MutableInteger mut = current.getValue();
if (mut.value > 1) {
mut.value--;
} else {
entryIterator.remove();
}
parent.size--;
canRemove = false;
}
}
//-----------------------------------------------------------------------
@Override
public int add(final E object, final int occurrences) {
if (occurrences < 0) {
throw new IllegalArgumentException("Occurrences must not be negative.");
}
final MutableInteger mut = map.get(object);
final int oldCount = mut != null ? mut.value : 0;
if (occurrences > 0) {
modCount++;
size += occurrences;
if (mut == null) {
map.put(object, new MutableInteger(occurrences));
} else {
mut.value += occurrences;
}
}
return oldCount;
}
//-----------------------------------------------------------------------
/**
* Clears the multiset by clearing the underlying map.
*/
@Override
public void clear() {
modCount++;
map.clear();
size = 0;
}
@Override
public int remove(final Object object, final int occurrences) {
if (occurrences < 0) {
throw new IllegalArgumentException("Occurrences must not be negative.");
}
final MutableInteger mut = map.get(object);
if (mut == null) {
return 0;
}
final int oldCount = mut.value;
if (occurrences > 0) {
modCount++;
if (occurrences < mut.value) {
mut.value -= occurrences;
size -= occurrences;
} else {
map.remove(object);
size -= mut.value;
mut.value = 0;
}
}
return oldCount;
}
//-----------------------------------------------------------------------
/**
* Mutable integer class for storing the data.
*/
protected static class MutableInteger {
/** The value of this mutable. */
protected int value;
/**
* Constructor.
* @param value the initial value
*/
MutableInteger(final int value) {
this.value = value;
}
@Override
public boolean equals(final Object obj) {
if (obj instanceof MutableInteger == false) {
return false;
}
return ((MutableInteger) obj).value == value;
}
@Override
public int hashCode() {
return value;
}
}
//-----------------------------------------------------------------------
@Override
protected Iterator createUniqueSetIterator() {
return new UniqueSetIterator<>(getMap().keySet().iterator(), this);
}
@Override
protected int uniqueElements() {
return map.size();
}
@Override
protected Iterator> createEntrySetIterator() {
return new EntrySetIterator<>(map.entrySet().iterator(), this);
}
//-----------------------------------------------------------------------
/**
* Inner class UniqueSetIterator.
*/
protected static class UniqueSetIterator extends AbstractIteratorDecorator {
/** The parent multiset */
protected final AbstractMapMultiSet parent;
/** The last returned element */
protected E lastElement = null;
/** Whether remove is allowed at present */
protected boolean canRemove = false;
/**
* Constructor.
* @param iterator the iterator to decorate
* @param parent the parent multiset
*/
protected UniqueSetIterator(final Iterator iterator, final AbstractMapMultiSet parent) {
super(iterator);
this.parent = parent;
}
@Override
public E next() {
lastElement = super.next();
canRemove = true;
return lastElement;
}
@Override
public void remove() {
if (canRemove == false) {
throw new IllegalStateException("Iterator remove() can only be called once after next()");
}
final int count = parent.getCount(lastElement);
super.remove();
parent.remove(lastElement, count);
lastElement = null;
canRemove = false;
}
}
/**
* Inner class EntrySetIterator.
*/
protected static class EntrySetIterator implements Iterator> {
/** The parent map */
protected final AbstractMapMultiSet parent;
protected final Iterator> decorated;
/** The last returned entry */
protected Entry last = null;
/** Whether remove is allowed at present */
protected boolean canRemove = false;
/**
* Constructor.
* @param iterator the iterator to decorate
* @param parent the parent multiset
*/
protected EntrySetIterator(final Iterator> iterator,
final AbstractMapMultiSet parent) {
this.decorated = iterator;
this.parent = parent;
}
@Override
public boolean hasNext() {
return decorated.hasNext();
}
@Override
public Entry next() {
last = new MultiSetEntry<>(decorated.next());
canRemove = true;
return last;
}
@Override
public void remove() {
if (canRemove == false) {
throw new IllegalStateException("Iterator remove() can only be called once after next()");
}
decorated.remove();
last = null;
canRemove = false;
}
}
/**
* Inner class MultiSetEntry.
*/
protected static class MultiSetEntry extends AbstractEntry {
protected final Map.Entry parentEntry;
/**
* Constructor.
* @param parentEntry the entry to decorate
*/
protected MultiSetEntry(final Map.Entry parentEntry) {
this.parentEntry = parentEntry;
}
@Override
public E getElement() {
return parentEntry.getKey();
}
@Override
public int getCount() {
return parentEntry.getValue().value;
}
}
//-----------------------------------------------------------------------
/**
* Write the multiset out using a custom routine.
* @param out the output stream
* @throws IOException any of the usual I/O related exceptions
*/
@Override
protected void doWriteObject(final ObjectOutputStream out) throws IOException {
out.writeInt(map.size());
for (final Map.Entry entry : map.entrySet()) {
out.writeObject(entry.getKey());
out.writeInt(entry.getValue().value);
}
}
/**
* Read the multiset in using a custom routine.
* @param in the input stream
* @throws IOException any of the usual I/O related exceptions
* @throws ClassNotFoundException if the stream contains an object which class can not be loaded
* @throws ClassCastException if the stream does not contain the correct objects
*/
@Override
protected void doReadObject(final ObjectInputStream in)
throws IOException, ClassNotFoundException {
final int entrySize = in.readInt();
for (int i = 0; i < entrySize; i++) {
@SuppressWarnings("unchecked") // This will fail at runtime if the stream is incorrect
final E obj = (E) in.readObject();
final int count = in.readInt();
map.put(obj, new MutableInteger(count));
size += count;
}
}
//-----------------------------------------------------------------------
/**
* Returns an array of all of this multiset's elements.
*
* @return an array of all of this multiset's elements
*/
@Override
public Object[] toArray() {
final Object[] result = new Object[size()];
int i = 0;
for (final Map.Entry entry : map.entrySet()) {
final E current = entry.getKey();
final MutableInteger count = entry.getValue();
for (int index = count.value; index > 0; index--) {
result[i++] = current;
}
}
return result;
}
/**
* 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.
*
* @param the type of the array elements
* @param array the array to populate
* @return 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
* @throws NullPointerException if the specified array is null
*/
@Override
public T[] toArray(T[] array) {
final int size = size();
if (array.length < size) {
@SuppressWarnings("unchecked") // safe as both are of type T
final T[] unchecked = (T[]) Array.newInstance(array.getClass().getComponentType(), size);
array = unchecked;
}
int i = 0;
for (final Map.Entry entry : map.entrySet()) {
final E current = entry.getKey();
final MutableInteger count = entry.getValue();
for (int index = count.value; index > 0; index--) {
// unsafe, will throw ArrayStoreException if types are not compatible, see javadoc
@SuppressWarnings("unchecked")
final T unchecked = (T) current;
array[i++] = unchecked;
}
}
while (i < array.length) {
array[i++] = null;
}
return array;
}
//-----------------------------------------------------------------------
@Override
public boolean equals(final Object object) {
if (object == this) {
return true;
}
if (object instanceof MultiSet == false) {
return false;
}
final MultiSet other = (MultiSet) object;
if (other.size() != size()) {
return false;
}
for (final E element : map.keySet()) {
if (other.getCount(element) != getCount(element)) {
return false;
}
}
return true;
}
@Override
public int hashCode() {
int total = 0;
for (final Map.Entry entry : map.entrySet()) {
final E element = entry.getKey();
final MutableInteger count = entry.getValue();
total += (element == null ? 0 : element.hashCode()) ^ count.value;
}
return total;
}
}