IndexedCollection.java
- /*
- * 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.collection;
- import java.util.Collection;
- import java.util.HashMap;
- import java.util.Iterator;
- import java.util.Objects;
- import java.util.function.Predicate;
- import org.apache.commons.collections4.MultiMap;
- import org.apache.commons.collections4.Transformer;
- import org.apache.commons.collections4.map.MultiValueMap;
- /**
- * An IndexedCollection is a Map-like view onto a Collection. It accepts a
- * keyTransformer to define how the keys are converted from the values.
- * <p>
- * Modifications made to this decorator modify the index as well as the
- * decorated {@link Collection}. However, modifications to the underlying
- * {@link Collection} will not update the index and it will get out of sync.
- * </p>
- * <p>
- * If modification of the decorated {@link Collection} is unavoidable, then a
- * call to {@link #reindex()} will update the index to the current contents of
- * the {@link Collection}.
- * </p>
- *
- * @param <K> the type of object in the index.
- * @param <C> the type of object in the collection.
- * @since 4.0
- */
- public class IndexedCollection<K, C> extends AbstractCollectionDecorator<C> {
- // TODO: replace with MultiValuedMap
- /** Serialization version */
- private static final long serialVersionUID = -5512610452568370038L;
- /**
- * Create an {@link IndexedCollection} for a non-unique index.
- *
- * @param <K> the index object type.
- * @param <C> the collection type.
- * @param coll the decorated {@link Collection}.
- * @param keyTransformer the {@link Transformer} for generating index keys.
- * @return the created {@link IndexedCollection}.
- */
- public static <K, C> IndexedCollection<K, C> nonUniqueIndexedCollection(final Collection<C> coll,
- final Transformer<C, K> keyTransformer) {
- return new IndexedCollection<>(coll, keyTransformer,
- MultiValueMap.<K, C>multiValueMap(new HashMap<>()),
- false);
- }
- /**
- * Create an {@link IndexedCollection} for a unique index.
- * <p>
- * If an element is added, which maps to an existing key, an {@link IllegalArgumentException}
- * will be thrown.
- *
- * @param <K> the index object type.
- * @param <C> the collection type.
- * @param coll the decorated {@link Collection}.
- * @param keyTransformer the {@link Transformer} for generating index keys.
- * @return the created {@link IndexedCollection}.
- */
- public static <K, C> IndexedCollection<K, C> uniqueIndexedCollection(final Collection<C> coll,
- final Transformer<C, K> keyTransformer) {
- return new IndexedCollection<>(coll, keyTransformer,
- MultiValueMap.<K, C>multiValueMap(new HashMap<>()),
- true);
- }
- /** The {@link Transformer} for generating index keys. */
- private final Transformer<C, K> keyTransformer;
- /** The map of indexes to collected objects. */
- private final MultiMap<K, C> index;
- /** The uniqueness constraint for the index. */
- private final boolean uniqueIndex;
- /**
- * Create a {@link IndexedCollection}.
- *
- * @param coll decorated {@link Collection}
- * @param keyTransformer {@link Transformer} for generating index keys
- * @param map map to use as index
- * @param uniqueIndex if the index shall enforce uniqueness of index keys
- */
- public IndexedCollection(final Collection<C> coll, final Transformer<C, K> keyTransformer,
- final MultiMap<K, C> map, final boolean uniqueIndex) {
- super(coll);
- this.keyTransformer = keyTransformer;
- this.index = map;
- this.uniqueIndex = uniqueIndex;
- reindex();
- }
- /**
- * {@inheritDoc}
- *
- * @throws IllegalArgumentException if the object maps to an existing key and the index
- * enforces a uniqueness constraint
- */
- @Override
- public boolean add(final C object) {
- final boolean added = super.add(object);
- if (added) {
- addToIndex(object);
- }
- return added;
- }
- @Override
- public boolean addAll(final Collection<? extends C> coll) {
- boolean changed = false;
- for (final C c: coll) {
- changed |= add(c);
- }
- return changed;
- }
- /**
- * Provides checking for adding the index.
- *
- * @param object the object to index
- * @throws IllegalArgumentException if the object maps to an existing key and the index
- * enforces a uniqueness constraint
- */
- private void addToIndex(final C object) {
- final K key = keyTransformer.apply(object);
- if (uniqueIndex && index.containsKey(key)) {
- throw new IllegalArgumentException("Duplicate key in uniquely indexed collection.");
- }
- index.put(key, object);
- }
- @Override
- public void clear() {
- super.clear();
- index.clear();
- }
- /**
- * {@inheritDoc}
- * <p>
- * Note: uses the index for fast lookup
- */
- @SuppressWarnings("unchecked")
- @Override
- public boolean contains(final Object object) {
- return index.containsKey(keyTransformer.apply((C) object));
- }
- /**
- * {@inheritDoc}
- * <p>
- * Note: uses the index for fast lookup
- */
- @Override
- public boolean containsAll(final Collection<?> coll) {
- for (final Object o : coll) {
- if (!contains(o)) {
- return false;
- }
- }
- return true;
- }
- /**
- * Gets the element associated with the given key.
- * <p>
- * In case of a non-unique index, this method will return the first
- * value associated with the given key. To retrieve all elements associated
- * with a key, use {@link #values(Object)}.
- *
- * @param key key to look up
- * @return element found
- * @see #values(Object)
- */
- public C get(final K key) {
- @SuppressWarnings("unchecked") // index is a MultiMap which returns a Collection
- final Collection<C> coll = (Collection<C>) index.get(key);
- return coll == null ? null : coll.iterator().next();
- }
- /**
- * Clears the index and re-indexes the entire decorated {@link Collection}.
- */
- public void reindex() {
- index.clear();
- for (final C c : decorated()) {
- addToIndex(c);
- }
- }
- @SuppressWarnings("unchecked")
- @Override
- public boolean remove(final Object object) {
- final boolean removed = super.remove(object);
- if (removed) {
- removeFromIndex((C) object);
- }
- return removed;
- }
- @Override
- public boolean removeAll(final Collection<?> coll) {
- boolean changed = false;
- for (final Object o : coll) {
- changed |= remove(o);
- }
- return changed;
- }
- /**
- * Removes an object from the index.
- *
- * @param object the object to remove
- */
- private void removeFromIndex(final C object) {
- index.remove(keyTransformer.apply(object));
- }
- /**
- * @since 4.4
- */
- @Override
- public boolean removeIf(final Predicate<? super C> filter) {
- if (Objects.isNull(filter)) {
- return false;
- }
- boolean changed = false;
- final Iterator<C> it = iterator();
- while (it.hasNext()) {
- if (filter.test(it.next())) {
- it.remove();
- changed = true;
- }
- }
- if (changed) {
- reindex();
- }
- return changed;
- }
- @Override
- public boolean retainAll(final Collection<?> coll) {
- final boolean changed = super.retainAll(coll);
- if (changed) {
- reindex();
- }
- return changed;
- }
- /**
- * Gets all elements associated with the given key.
- *
- * @param key key to look up
- * @return a collection of elements found, or null if {@code contains(key) == false}
- */
- @SuppressWarnings("unchecked") // index is a MultiMap which returns a Collection
- public Collection<C> values(final K key) {
- return (Collection<C>) index.get(key);
- }
- }