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Commons Collections example source code file (GrowthList.java)

This example Commons Collections source code file (GrowthList.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

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);
    }

}

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