CollectionBag.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.bag;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.Collection;
import java.util.Iterator;
import org.apache.commons.collections4.Bag;
/**
* Decorates another {@link Bag} to comply with the Collection contract.
* <p>
* By decorating an existing {@link Bag} instance with a {@link CollectionBag},
* it can be safely passed on to methods that require Collection types that
* are fully compliant with the Collection contract.
* </p>
* <p>
* The method Javadoc highlights the differences compared to the original Bag interface.
* </p>
*
* @see Bag
* @param <E> the type of elements in this bag
* @since 4.0
*/
public final class CollectionBag<E> extends AbstractBagDecorator<E> {
/** Serialization version */
private static final long serialVersionUID = -2560033712679053143L;
/**
* Factory method to create a bag that complies to the Collection contract.
*
* @param <E> the type of the elements in the bag
* @param bag the bag to decorate, must not be null
* @return a Bag that complies to the Collection contract
* @throws NullPointerException if bag is null
*/
public static <E> Bag<E> collectionBag(final Bag<E> bag) {
return new CollectionBag<>(bag);
}
/**
* Constructor that wraps (not copies).
*
* @param bag the bag to decorate, must not be null
* @throws NullPointerException if bag is null
*/
public CollectionBag(final Bag<E> bag) {
super(bag);
}
/**
* <i>(Change)</i>
* Adds one copy of the specified object to the Bag.
* <p>
* Since this method always increases the size of the bag, it
* will always return {@code true}.
*
* @param object the object to add
* @return {@code true}, always
*/
@Override
public boolean add(final E object) {
return add(object, 1);
}
/**
* <i>(Change)</i>
* Adds {@code count} copies of the specified object to the Bag.
* <p>
* Since this method always increases the size of the bag, it
* will always return {@code true}.
*
* @param object the object to add
* @param count the number of copies to add
* @return {@code true}, always
*/
@Override
public boolean add(final E object, final int count) {
decorated().add(object, count);
return true;
}
// Collection interface
@Override
public boolean addAll(final Collection<? extends E> coll) {
boolean changed = false;
for (final E current : coll) {
final boolean added = add(current, 1);
changed = changed || added;
}
return changed;
}
/**
* <i>(Change)</i>
* Returns {@code true} if the bag contains all elements in
* the given collection, <b>not</b> respecting cardinality. That is,
* if the given collection {@code coll} contains at least one of
* every object contained in this object.
*
* @param coll the collection to check against
* @return {@code true} if the Bag contains at least one of every object in the collection
*/
@Override
public boolean containsAll(final Collection<?> coll) {
return coll.stream().allMatch(this::contains);
}
/**
* Read the collection 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
* @throws ClassCastException if deserialized object has wrong type
*/
@SuppressWarnings("unchecked") // will throw CCE, see Javadoc
private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
in.defaultReadObject();
setCollection((Collection<E>) in.readObject());
}
/**
* <i>(Change)</i>
* Removes the first occurrence of the given object from the bag.
* <p>
* This will also remove the object from the {@link #uniqueSet()} if the
* bag contains no occurrence anymore of the object after this operation.
*
* @param object the object to remove
* @return {@code true} if this call changed the collection
*/
@Override
public boolean remove(final Object object) {
return remove(object, 1);
}
/**
* <i>(Change)</i>
* Remove all elements represented in the given collection,
* <b>not</b> respecting cardinality. That is, remove <i>all</i>
* occurrences of every object contained in the given collection.
*
* @param coll the collection to remove
* @return {@code true} if this call changed the collection
*/
@Override
public boolean removeAll(final Collection<?> coll) {
if (coll != null) {
boolean result = false;
for (final Object obj : coll) {
final boolean changed = remove(obj, getCount(obj));
result = result || changed;
}
return result;
}
// let the decorated bag handle the case of null argument
return decorated().removeAll(null);
}
/**
* <i>(Change)</i>
* Remove any members of the bag that are not in the given collection,
* <i>not</i> respecting cardinality. That is, any object in the given
* collection {@code coll} will be retained in the bag with the same
* number of copies prior to this operation. All other objects will be
* completely removed from this bag.
* <p>
* This implementation iterates over the elements of this bag, checking
* each element in turn to see if it's contained in {@code coll}.
* If it's not contained, it's removed from this bag. As a consequence,
* it is advised to use a collection type for {@code coll} that provides
* a fast (e.g. O(1)) implementation of {@link Collection#contains(Object)}.
*
* @param coll the collection to retain
* @return {@code true} if this call changed the collection
*/
@Override
public boolean retainAll(final Collection<?> coll) {
if (coll != null) {
boolean modified = false;
final Iterator<E> e = iterator();
while (e.hasNext()) {
if (!coll.contains(e.next())) {
e.remove();
modified = true;
}
}
return modified;
}
// let the decorated bag handle the case of null argument
return decorated().retainAll(null);
}
// Bag interface
/**
* Write the collection 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();
out.writeObject(decorated());
}
}