/*  * Copyright 2004-2005 OpenSymphony  *  * 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. *  *//* * Previously Copyright (c) 2001-2004 James House */package org.quartz.simpl;import org.apache.commons.logging.Log;import org.apache.commons.logging.LogFactory;import org.quartz.SchedulerConfigException;import org.quartz.spi.ThreadPool;/** * <p> * This is class is a simple implementation of a zero size thread pool, based on the * <code>{@link org.quartz.spi.ThreadPool}</code> interface. * </p> *  * <p> * The pool has zero <code>Thread</code>s and does not grow or shrink based on demand. * Which means it is obviously not useful for most scenarios.  When it may be useful * is to prevent creating any worker threads at all - which may be desirable for * the sole purpose of preserving system resources in the case where the scheduler * instance only exists in order to schedule jobs, but which will never execute * jobs (e.g. will never have start() called on it). * </p> *  * <p> * </p> *  * @author Wayne Fay */public class ZeroSizeThreadPool implements ThreadPool {    /*     * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~     *      * Data members.     *      * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~     */    private final Log log = LogFactory.getLog(getClass());    /*     * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~     *      * Constructors.     *      * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~     */    /**     * <p>     * Create a new <code>ZeroSizeThreadPool</code>.     * </p>     */    public ZeroSizeThreadPool() {    }    /*     * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~     *      * Interface.     *      * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~     */    public Log getLog() {        return log;    }    public int getPoolSize() {        return 0;    }    public void initialize() throws SchedulerConfigException {    }    public void shutdown() {        shutdown(true);    }    public void shutdown(boolean waitForJobsToComplete) {        getLog().debug("shutdown complete");    }    public boolean runInThread(Runnable runnable) {        throw new UnsupportedOperationException("This ThreadPool should not be used on Scheduler instances that are start()ed.");    }    public int blockForAvailableThreads() {        throw new UnsupportedOperationException("This ThreadPool should not be used on Scheduler instances that are start()ed.");    }}