LazyListManager implementation from Chet Haase. Read more here: http://graphics-geek.blogspot.de/2013/09/lazy-lists.html.

LazyListManager

/*
 * Copyright (C) 2013 The Android Open Source Project
 *
 * 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.
 */

import java.util.ArrayList;
import java.util.List;

public class LazyListManager {

    public static <T> List<T> add(List<T> list, T item) {
        if (list == null) {
            list = new ArrayList<T>();
            list.add(item);
        } else if (!list.contains(item)) {
            list.add(item);
        }
        return list;
    }

    public static <T> List<T> remove(List<T> list, T item) {
        if (list != null) {
            list.remove(item);
            if (list.isEmpty()) {
                list = null;
            }
        }
        return list;
    }
}