compositecollection.java

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/*
 *  Copyright 2001-2004 The Apache Software Foundation
 *
 *  Licensed 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.collections.collection;

import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;

import org.apache.commons.collections.iterators.EmptyIterator;
import org.apache.commons.collections.iterators.IteratorChain;
import org.apache.commons.collections.list.UnmodifiableList;

/**
 * Decorates a collection of other collections to provide a single unified view.
 * <p>
 * Changes made to this collection will actually be made on the decorated collection.
 * Add and remove operations require the use of a pluggable strategy. If no 
 * strategy is provided then add and remove are unsupported.
 *
 * @since Commons Collections 3.0
 * @version $Revision: 155406 $ $Date: 2005-02-26 12:55:26 +0000 (Sat, 26 Feb 2005) $
 *
 * @author Brian McCallister
 * @author Stephen Colebourne
 * @author Phil Steitz
 */
public class CompositeCollection implements Collection {
    
    /** CollectionMutator to handle changes to the collection */
    protected CollectionMutator mutator;
    
    /** Collections in the composite */
    protected Collection[] all;
    
    /**
     * Create an empty CompositeCollection.
     */
    public CompositeCollection() {
        super();
        this.all = new Collection[0];
    }
    
    /**
     * Create a Composite Collection with only coll composited.
     * 
     * @param coll  a collection to decorate
     */
    public CompositeCollection(Collection coll) {
        this();
        this.addComposited(coll);
    }
    
    /**
     * Create a CompositeCollection with colls as the initial list of
     * composited collections.
     * 
     * @param colls  an array of collections to decorate
     */
    public CompositeCollection(Collection[] colls) {
        this();
        this.addComposited(colls);
    }
    
    //-----------------------------------------------------------------------
    /**
     * Gets the size of this composite collection.
     * <p>
     * This implementation calls <code>size()</code> on each collection.
     *
     * @return total number of elements in all contained containers
     */
    public int size() {
        int size = 0;
        for (int i = this.all.length - 1; i >= 0; i--) {
            size += this.all[i].size();
        }
        return size;
    }
    
    /**
     * Checks whether this composite collection is empty.
     * <p>
     * This implementation calls <code>isEmpty()</code> on each collection.
     *
     * @return true if all of the contained collections are empty
     */
    public boolean isEmpty() {
        for (int i = this.all.length - 1; i >= 0; i--) {
            if (this.all[i].isEmpty() == false) {
                return false;
            }
        }
        return true;
    }
    
    /**
     * Checks whether this composite collection contains the object.
     * <p>
     * This implementation calls <code>contains()</code> on each collection.
     *
     * @param obj  the object to search for
     * @return true if obj is contained in any of the contained collections
     */
    public boolean contains(Object obj) {
        for (int i = this.all.length - 1; i >= 0; i--) {
            if (this.all[i].contains(obj)) {
                return true;
            }
        }
        return false;
    }
    
    /**
     * Gets an iterator over all the collections in this composite.
     * <p>
     * This implementation uses an <code>IteratorChain</code>.
     *
     * @return an <code>IteratorChain</code> instance which supports
     *  <code>remove()</code>. Iteration occurs over contained collections in
     *  the order they were added, but this behavior should not be relied upon.
     * @see IteratorChain
     */
    public Iterator iterator() {
        if (this.all.length == 0) {
            return EmptyIterator.INSTANCE;
        }
        IteratorChain chain = new IteratorChain();
        for (int i = 0; i < this.all.length; ++i) {
            chain.addIterator(this.all[i].iterator());
        }
        return chain;
    }
    
    /**
     * Returns an array containing all of the elements in this composite.
     *
     * @return an object array of all the elements in the collection
     */
    public Object[] toArray() {
        final Object[] result = new Object[this.size()];
        int i = 0;
        for (Iterator it = this.iterator(); it.hasNext(); i++) {
            result[i] = it.next();
        }
        return result;
    }
    
    /**
     * Returns an object array, populating the supplied array if possible.
     * See <code>Collection</code> interface for full details.
     *
     * @param array  the array to use, populating if possible
     * @return an array of all the elements in the collection
     */
    public Object[] toArray(Object[] array) {
        int size = this.size();
        Object[] result = null;
        if (array.length >= size) {
            result = array;
        }
        else {
            result = (Object[]) Array.newInstance(array.getClass().getComponentType(), size);
        }
        
        int offset = 0;
        for (int i = 0; i < this.all.length; ++i) {
            for (Iterator it = this.all[i].iterator(); it.hasNext();) {
                result[offset++] = it.next();
            }
        }
        if (result.length > size) {
            result[size] = null;
        }
        return result;
    }
    
    /**
     * Adds an object to the collection, throwing UnsupportedOperationException
     * unless a CollectionMutator strategy is specified.
     *
     * @param obj  the object to add
     * @return true if the collection was modified
     * @throws UnsupportedOperationException if CollectionMutator hasn't been set
     * @throws UnsupportedOperationException if add is unsupported
     * @throws ClassCastException if the object cannot be added due to its type
     * @throws NullPointerException if the object cannot be added because its null
     * @throws IllegalArgumentException if the object cannot be added
     */
    public boolean add(Object obj) {
        if (this.mutator == null) {
           throw new UnsupportedOperationException(
           "add() is not supported on CompositeCollection without a CollectionMutator strategy");
        }
        return this.mutator.add(this, this.all, obj);
    }
    
    /**
     * Removes an object from the collection, throwing UnsupportedOperationException
     * unless a CollectionMutator strategy is specified.
     *
     * @param obj  the object being removed
     * @return true if the collection is changed
     * @throws UnsupportedOperationException if removed is unsupported
     * @throws ClassCastException if the object cannot be removed due to its type
     * @throws NullPointerException if the object cannot be removed because its null
     * @throws IllegalArgumentException if the object cannot be removed
     */