001/**
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.activemq.util;
018
019/**
020 * A very simple stop watch.
021 * <p/>
022 * This implementation is not thread safe and can only time one task at any given time.
023 *
024 * @version
025 */
026public final class StopWatch {
027
028    private long start;
029    private long stop;
030
031    /**
032     * Starts the stop watch
033     */
034    public StopWatch() {
035        this(true);
036    }
037
038    /**
039     * Creates the stop watch
040     *
041     * @param started whether it should start immediately
042     */
043    public StopWatch(boolean started) {
044        if (started) {
045            restart();
046        }
047    }
048
049    /**
050     * Starts or restarts the stop watch
051     */
052    public void restart() {
053        start = System.currentTimeMillis();
054        stop = 0;
055    }
056
057    /**
058     * Stops the stop watch
059     *
060     * @return the time taken in millis.
061     */
062    public long stop() {
063        stop = System.currentTimeMillis();
064        return taken();
065    }
066
067    /**
068     * Returns the time taken in millis.
069     *
070     * @return time in millis
071     */
072    public long taken() {
073        if (start > 0 && stop > 0) {
074            return stop - start;
075        } else if (start > 0) {
076            return System.currentTimeMillis() - start;
077        } else {
078            return 0;
079        }
080    }
081}