Commons Collections example source code file (GrowthList.java)

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Java - Commons Collections tags/keywords

abstractserializablelistdecorator, abstractserializablelistdecorator, arraylist, arraylist, collection, growthlist, growthlist, list, object, object, util

The Commons Collections GrowthList.java source code

/*
 *  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.collections.list;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;

/**
 * Decorates another <code>List to make it seamlessly grow when
 * indices larger than the list size are used on add and set,
 * avoiding most IndexOutOfBoundsExceptions.
 * <p>
 * This class avoids errors by growing when a set or add method would
 * normally throw an IndexOutOfBoundsException.
 * Note that IndexOutOfBoundsException IS returned for invalid negative indices.
 * <p>
 * Trying to set or add to an index larger than the size will cause the list
 * to grow (using <code>null elements). Clearly, care must be taken
 * not to use excessively large indices, as the internal list will grow to
 * match.
 * <p>
 * Trying to use any method other than add or set with an invalid index will
 * call the underlying list and probably result in an IndexOutOfBoundsException.
 * <p>
 * Take care when using this list with <code>null values, as
 * <code>null is the value added when growing the list.
 * <p>
 * All sub-lists will access the underlying list directly, and will throw
 * IndexOutOfBoundsExceptions.
 * <p>
 * This class differs from {@link LazyList} because here growth occurs on
 * set and add, where <code>LazyList grows on get. However, they
 * can be used together by decorating twice.
 *
 * @see LazyList
 * @since Commons Collections 3.2
 * @version $Revision: 155406 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
 *
 * @author Stephen Colebourne
 * @author Paul Legato
 */
public class GrowthList extends AbstractSerializableListDecorator {

    /** Serialization version */
    private static final long serialVersionUID = -3620001881672L;

    /**
     * Factory method to create a growth list.
     *
     * @param list  the list to decorate, must not be null
     * @throws IllegalArgumentException if list is null
     */
    public static List decorate(List list) {
        return new GrowthList(list);
    }

    //-----------------------------------------------------------------------
    /**
     * Constructor that uses an ArrayList internally.
     */
    public GrowthList() {
        super(new ArrayList());
    }

    /**
     * Constructor that uses an ArrayList internally.
     *
     * @param initialSize  the initial size of the ArrayList
     * @throws IllegalArgumentException if initial size is invalid
     */
    public GrowthList(int initialSize) {
        super(new ArrayList(initialSize));
    }

    /**
     * Constructor that wraps (not copies).
     *
     * @param list  the list to decorate, must not be null
     * @throws IllegalArgumentException if list is null
     */
    protected GrowthList(List list) {
        super(list);
    }

    //-----------------------------------------------------------------------
    /**
     * Decorate the add method to perform the growth behaviour.
     * <p>
     * If the requested index is greater than the current size, the list will
     * grow to the new size. Indices between the old size and the requested
     * size will be filled with <code>null.
     * <p>
     * If the index is less than the current size, the value will be added to
     * the underlying list directly.
     * If the index is less than zero, the underlying list is called, which
     * will probably throw an IndexOutOfBoundsException.
     *
     * @param index  the index to add at
     * @param element  the object to add at the specified index
     * @throws UnsupportedOperationException if the underlying list doesn't implement set
     * @throws ClassCastException if the underlying list rejects the element
     * @throws IllegalArgumentException if the underlying list rejects the element
     */
    public void add(int index, Object element) {
        int size = getList().size();
        if (index > size) {
            getList().addAll(Collections.nCopies(index - size, null));
        }
        getList().add(index, element);
    }

    //-----------------------------------------------------------------------
    /**
     * Decorate the addAll method to perform the growth behaviour.
     * <p>
     * If the requested index is greater than the current size, the list will
     * grow to the new size. Indices between the old size and the requested
     * size will be filled with <code>null.
     * <p>
     * If the index is less than the current size, the values will be added to
     * the underlying list directly.
     * If the index is less than zero, the underlying list is called, which
     * will probably throw an IndexOutOfBoundsException.
     *
     * @param index  the index to add at
     * @param coll  the collection to add at the specified index
     * @return true if the list changed
     * @throws UnsupportedOperationException if the underlying list doesn't implement set
     * @throws ClassCastException if the underlying list rejects the element
     * @throws IllegalArgumentException if the underlying list rejects the element
     */
    public boolean addAll(int index, Collection coll) {
        int size = getList().size();
        boolean result = false;
        if (index > size) {
            getList().addAll(Collections.nCopies(index - size, null));
            result = true;
        }
        return (getList().addAll(index, coll) | result);
    }

    //-----------------------------------------------------------------------
    /**
     * Decorate the set method to perform the growth behaviour.
     * <p>
     * If the requested index is greater than the current size, the list will
     * grow to the new size. Indices between the old size and the requested
     * size will be filled with <code>null.
     * <p>
     * If the index is less than the current size, the value will be set onto
     * the underlying list directly.
     * If the index is less than zero, the underlying list is called, which
     * will probably throw an IndexOutOfBoundsException.
     *
     * @param index  the index to set
     * @param element  the object to set at the specified index
     * @return the object previously at that index
     * @throws UnsupportedOperationException if the underlying list doesn't implement set
     * @throws ClassCastException if the underlying list rejects the element
     * @throws IllegalArgumentException if the underlying list rejects the element
     */
    public Object set(int index, Object element) {
        int size = getList().size();
        if (index >= size) {
            getList().addAll(Collections.nCopies((index - size) + 1, null));
        }
        return getList().set(index, element);
    }

}