# UnboundedQueue.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.synapse.commons.executors.queues;

    import org.apache.synapse.commons.executors.InternalQueue;

    import java.util.*;
    import java.util.concurrent.locks.Condition;

    /**
     * An unbounded queue backed by and ArrayList.
     * @param <E>
     */
    public class UnboundedQueue<E> extends AbstractQueue<E> implements InternalQueue<E> {

        private List<E> elements = new ArrayList<E>();

         /**
         * Priority of this queue
         */
        private int priority;

        /**
         * A waiting queue when this queue is full
         */
        private Condition notFullCond;

        public UnboundedQueue(int priority) {
            this.priority = priority;
        }

        public Iterator<E> iterator() {
            return elements.iterator();
        }

        public int size() {
            return elements.size();
        }

        public boolean offer(E e) {
            return elements.add(e);
        }

        public E poll() {
            if (elements.size() > 0) {
                return elements.remove(elements.size() - 1);
            }
            return null;
        }

        public E peek() {
            if (elements.size() > 0) {
                return elements.get(elements.size() - 1);
            }
            return null;
        }

        public int getPriority() {
            return priority;
        }

        public void setPriority(int p) {
            this.priority = p;
        }

        public Condition getNotFullCond() {
            return notFullCond;
        }

        public void setNotFullCond(Condition condition) {
            this.notFullCond = condition;
        }

        public int drainTo(Collection<? super E> c) {
            int count = elements.size();
            c.addAll(elements);
            elements.clear();
            return count;
        }

        public int drainTo(Collection<? super E> c, int maxElements) {
            if (maxElements >= elements.size()) {
                return drainTo(c);
            } else {
                elements.subList(elements.size() - maxElements - 1, elements.size());
                return maxElements;
            }
        }

        public int remainingCapacity() {
            return Integer.MAX_VALUE;
        }

        public int getCapacity() {
            return Integer.MAX_VALUE;
        }

        @Override
        public boolean contains(Object o) {
            return elements.contains(o);
        }

        @Override
        public boolean remove(Object o) {
            return elements.remove(o);
        }
    }