StopWatch provides a convenient API for timings.
import java.util.Date;
/*
* 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.
*/
/**
* <p>
* <code>StopWatch</code> provides a convenient API for timings.
* </p>
*
* <p>
* To start the watch, call {@link #start()}. At this point you can:
* </p>
* <ul>
* <li>{@link #split()} the watch to get the time whilst the watch continues in the background. {@link #unsplit()} will
* remove the effect of the split. At this point, these three options are available again.</li>
* <li>{@link #suspend()} the watch to pause it. {@link #resume()} allows the watch to continue. Any time between the
* suspend and resume will not be counted in the total. At this point, these three options are available again.</li>
* <li>{@link #stop()} the watch to complete the timing session.</li>
* </ul>
*
* <p>
* It is intended that the output methods {@link #toString()} and {@link #getTime()} should only be called after stop,
* split or suspend, however a suitable result will be returned at other points.
* </p>
*
* <p>
* NOTE: As from v2.1, the methods protect against inappropriate calls. Thus you cannot now call stop before start,
* resume before suspend or unsplit before split.
* </p>
*
* <p>
* 1. split(), suspend(), or stop() cannot be invoked twice<br />
* 2. unsplit() may only be called if the watch has been split()<br />
* 3. resume() may only be called if the watch has been suspend()<br />
* 4. start() cannot be called twice without calling reset()
* </p>
*
* @author Stephen Colebourne
* @since 2.0
* @version $Id: StopWatch.java 583608 2007-10-10 20:38:41Z ggregory $
*/
public class StopWatch {
// running states
private static final int STATE_UNSTARTED = 0;
private static final int STATE_RUNNING = 1;
private static final int STATE_STOPPED = 2;
private static final int STATE_SUSPENDED = 3;
// split state
private static final int STATE_UNSPLIT = 10;
private static final int STATE_SPLIT = 11;
/**
* The current running state of the StopWatch.
*/
private int runningState = STATE_UNSTARTED;
/**
* Whether the stopwatch has a split time recorded.
*/
private int splitState = STATE_UNSPLIT;
/**
* The start time.
*/
private long startTime = -1;
/**
* The stop time.
*/
private long stopTime = -1;
/**
* <p>
* Constructor.
* </p>
*/
public StopWatch() {
super();
}
/**
* <p>
* Start the stopwatch.
* </p>
*
* <p>
* This method starts a new timing session, clearing any previous values.
* </p>
*
* @throws IllegalStateException
* if the StopWatch is already running.
*/
public void start() {
if (this.runningState == STATE_STOPPED) {
throw new IllegalStateException("Stopwatch must be reset before being restarted. ");
}
if (this.runningState != STATE_UNSTARTED) {
throw new IllegalStateException("Stopwatch already started. ");
}
this.stopTime = -1;
this.startTime = System.currentTimeMillis();
this.runningState = STATE_RUNNING;
}
/**
* <p>
* Stop the stopwatch.
* </p>
*
* <p>
* This method ends a new timing session, allowing the time to be retrieved.
* </p>
*
* @throws IllegalStateException
* if the StopWatch is not running.
*/
public void stop() {
if (this.runningState != STATE_RUNNING && this.runningState != STATE_SUSPENDED) {
throw new IllegalStateException("Stopwatch is not running. ");
}
if (this.runningState == STATE_RUNNING) {
this.stopTime = System.currentTimeMillis();
}
this.runningState = STATE_STOPPED;
}
/**
* <p>
* Resets the stopwatch. Stops it if need be.
* </p>
*
* <p>
* This method clears the internal values to allow the object to be reused.
* </p>
*/
public void reset() {
this.runningState = STATE_UNSTARTED;
this.splitState = STATE_UNSPLIT;
this.startTime = -1;
this.stopTime = -1;
}
/**
* <p>
* Split the time.
* </p>
*
* <p>
* This method sets the stop time of the watch to allow a time to be extracted. The start time is unaffected,
* enabling {@link #unsplit()} to continue the timing from the original start point.
* </p>
*
* @throws IllegalStateException
* if the StopWatch is not running.
*/
public void split() {
if (this.runningState != STATE_RUNNING) {
throw new IllegalStateException("Stopwatch is not running. ");
}
this.stopTime = System.currentTimeMillis();
this.splitState = STATE_SPLIT;
}
/**
* <p>
* Remove a split.
* </p>
*
* <p>
* This method clears the stop time. The start time is unaffected, enabling timing from the original start point to
* continue.
* </p>
*
* @throws IllegalStateException
* if the StopWatch has not been split.
*/
public void unsplit() {
if (this.splitState != STATE_SPLIT) {
throw new IllegalStateException("Stopwatch has not been split. ");
}
this.stopTime = -1;
this.splitState = STATE_UNSPLIT;
}
/**
* <p>
* Suspend the stopwatch for later resumption.
* </p>
*
* <p>
* This method suspends the watch until it is resumed. The watch will not include time between the suspend and
* resume calls in the total time.
* </p>
*
* @throws IllegalStateException
* if the StopWatch is not currently running.
*/
public void suspend() {
if (this.runningState != STATE_RUNNING) {
throw new IllegalStateException("Stopwatch must be running to suspend. ");
}
this.stopTime = System.currentTimeMillis();
this.runningState = STATE_SUSPENDED;
}
/**
* <p>
* Resume the stopwatch after a suspend.
* </p>
*
* <p>
* This method resumes the watch after it was suspended. The watch will not include time between the suspend and
* resume calls in the total time.
* </p>
*
* @throws IllegalStateException
* if the StopWatch has not been suspended.
*/
public void resume() {
if (this.runningState != STATE_SUSPENDED) {
throw new IllegalStateException("Stopwatch must be suspended to resume. ");
}
this.startTime += (System.currentTimeMillis() - this.stopTime);
this.stopTime = -1;
this.runningState = STATE_RUNNING;
}
/**
* <p>
* Get the time on the stopwatch.
* </p>
*
* <p>
* This is either the time between the start and the moment this method is called, or the amount of time between
* start and stop.
* </p>
*
* @return the time in milliseconds
*/
public long getTime() {
if (this.runningState == STATE_STOPPED || this.runningState == STATE_SUSPENDED) {
return this.stopTime - this.startTime;
} else if (this.runningState == STATE_UNSTARTED) {
return 0;
} else if (this.runningState == STATE_RUNNING) {
return System.currentTimeMillis() - this.startTime;
}
throw new RuntimeException("Illegal running state has occured. ");
}
/**
* <p>
* Get the split time on the stopwatch.
* </p>
*
* <p>
* This is the time between start and latest split.
* </p>
*
* @return the split time in milliseconds
*
* @throws IllegalStateException
* if the StopWatch has not yet been split.
* @since 2.1
*/
public long getSplitTime() {
if (this.splitState != STATE_SPLIT) {
throw new IllegalStateException("Stopwatch must be split to get the split time. ");
}
return this.stopTime - this.startTime;
}
/**
* Returns the time this stopwatch was started.
*
* @return the time this stopwatch was started
* @throws IllegalStateException
* if this StopWatch has not been started
* @since 2.4
*/
public long getStartTime() {
if (this.runningState == STATE_UNSTARTED) {
throw new IllegalStateException("Stopwatch has not been started");
}
return this.startTime;
}
/**
* <p>
* Gets a summary of the time that the stopwatch recorded as a string.
* </p>
*
* <p>
* The format used is ISO8601-like, <i>hours</i>:<i>minutes</i>:<i>seconds</i>.<i>milliseconds</i>.
* </p>
*
* @return the time as a String
*/
public String toString() {
return new Date(getTime()).toString();
}
/**
* <p>
* Gets a summary of the split time that the stopwatch recorded as a string.
* </p>
*
* <p>
* The format used is ISO8601-like, <i>hours</i>:<i>minutes</i>:<i>seconds</i>.<i>milliseconds</i>.
* </p>
*
* @return the split time as a String
* @since 2.1
*/
public String toSplitString() {
return new Date(getSplitTime()).toString();
}
}
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