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     */
017    package 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     */
026    public 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    }