leap.lang.time.StopWatch Maven / Gradle / Ivy
/*
* 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 leap.lang.time;
/**
*
* StopWatch provides a convenient API for timings.
*
*
*
* To start the watch, call {@link #start()}. At this point you can:
*
*
* - {@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.
* - {@link #stop()} the watch to complete the timing session.
*
*
*
* It is intended that the output methods {@link #toString()} and {@link #getElapsedMilliseconds()} should only be called after stop,
* split or suspend, however a suitable result will be returned at other points.
*
*
*
* 1. split(), suspend(), or stop() cannot be invoked twice
* 2. resume() may only be called if the watch has been suspend()
* 3. start() cannot be called twice without calling reset()
*
*
*
* This class is not thread-safe
*
*/
public class StopWatch {
private static final long NANO_2_MILLIS = 1000000L;
// 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;
/**
* The current running state of the StopWatch.
*/
private int state = STATE_UNSTARTED;
/**
* The start time.
*/
private long startTime;
/**
* The start time in Millis - nanoTime is only for elapsed time so we need to also store the currentTimeMillis to
* maintain the old getStartTime API.
*/
private long startTimeMillis;
/**
* The stop time.
*/
private long stopTime;
/**
* create {@link StopWatch} instance and call {@link #start()}
*
* @return the {@link StopWatch} instance aleady started.
*/
public static StopWatch startNew(){
StopWatch sw = new StopWatch();
sw.start();
return sw;
}
public StopWatch() {
}
/**
*
* Start the stopwatch.
*
*
*
* This method starts a new timing session, clearing any previous values.
*
*
* @throws IllegalStateException if the StopWatch is already running.
*/
public StopWatch start() {
if (this.state == STATE_STOPPED) {
throw new IllegalStateException("Stopwatch must be reset before being restarted. ");
}
if (this.state != STATE_UNSTARTED) {
throw new IllegalStateException("Stopwatch already started. ");
}
this.startTime = System.nanoTime();
this.startTimeMillis = System.currentTimeMillis();
this.state = STATE_RUNNING;
return this;
}
/**
*
* Stop the stopwatch.
*
*
*
* This method ends a new timing session, allowing the time to be retrieved.
*
*
* @throws IllegalStateException if the StopWatch is not running.
*/
public StopWatch stop() {
if (this.state != STATE_RUNNING && this.state != STATE_SUSPENDED) {
throw new IllegalStateException("Stopwatch is not running. ");
}
if (this.state == STATE_RUNNING) {
this.stopTime = System.nanoTime();
}
this.state = STATE_STOPPED;
return this;
}
/**
*
* Resets the stopwatch. Stops it if need be.
*
*
*
* This method clears the internal values to allow the object to be reused.
*
*/
public StopWatch reset() {
this.state = STATE_UNSTARTED;
return this;
}
/**
* Stops time interval measurement, resets the elapsed time to zero, and starts measuring elapsed time
*/
public StopWatch restart(){
reset();
start();
return this;
}
/**
*
* Suspend the stopwatch for later resumption.
*
*
*
* 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.
*
*
* @throws IllegalStateException if the StopWatch is not currently running.
*/
public StopWatch suspend() {
if (this.state != STATE_RUNNING) {
throw new IllegalStateException("Stopwatch must be running to suspend. ");
}
this.stopTime = System.nanoTime();
this.state = STATE_SUSPENDED;
return this;
}
/**
*
* Resume the stopwatch after a suspend.
*
*
*
* 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.
*
*
* @throws IllegalStateException if the StopWatch has not been suspended.
*/
public StopWatch resume() {
if (this.state != STATE_SUSPENDED) {
throw new IllegalStateException("Stopwatch must be suspended to resume. ");
}
this.startTime += System.nanoTime() - this.stopTime;
this.state = STATE_RUNNING;
return this;
}
/**
*
* Get the milliseconds time on the stopwatch.
*
*
*
* This is either the time between the start and the moment this method is called, or the amount of time between
* start and stop.
*
*
* @return the time in milliseconds
*/
public long getElapsedMilliseconds() {
return getElapsedNanoseconds() / NANO_2_MILLIS;
}
/**
*
* Get the time on the stopwatch in nanoseconds.
*
*
*
* This is either the time between the start and the moment this method is called, or the amount of time between
* start and stop.
*
*
* @return the time in nanoseconds
*/
public long getElapsedNanoseconds() {
if (this.state == STATE_STOPPED || this.state == STATE_SUSPENDED) {
return this.stopTime - this.startTime;
} else if (this.state == STATE_UNSTARTED) {
return 0;
} else if (this.state == STATE_RUNNING) {
return System.nanoTime() - this.startTime;
}
throw new IllegalStateException("Illegal running state has occured. ");
}
/**
* Returns the time this stopwatch was started.
*
* @return the time this stopwatch was started
*
* @throws IllegalStateException if this StopWatch has not been started
*/
public long getStartTime() {
if (this.state == STATE_UNSTARTED) {
throw new IllegalStateException("Stopwatch has not been started");
}
// System.nanoTime is for elapsed time
return this.startTimeMillis;
}
/**
*
* Gets a summary of the time that the stopwatch recorded as a string.
*
*
* @return the time as a String
*/
@Override
public String toString() {
return getElapsedMilliseconds() + "ms";
}
}