Java中有秒表吗？

Java中有秒表吗？在Google上，我只找到无法使用的秒表代码-它们总是返回0毫秒。

我发现的这段代码行不通，但我不明白为什么。

public class StopWatch {

  private long startTime = 0;
  private long stopTime = 0;
  private boolean running = false;


  public void start() {
    this.startTime = System.currentTimeMillis();
    this.running = true;
  }


  public void stop() {
    this.stopTime = System.currentTimeMillis();
    this.running = false;
  }


  //elaspsed time in milliseconds
  public long getElapsedTime() {
    long elapsed;
    if (running) {
      elapsed = (System.currentTimeMillis() - startTime);
    } else {
      elapsed = (stopTime - startTime);
    }
    return elapsed;
  }


  //elaspsed time in seconds
  public long getElapsedTimeSecs() {
    long elapsed;
    if (running) {
      elapsed = ((System.currentTimeMillis() - startTime) / 1000);
    } else {
      elapsed = ((stopTime - startTime) / 1000);
    }
    return elapsed;
  }
}

您会在其中找到一个

http://commons.apache.org/lang/

叫做

org.apache.commons.lang.time.StopWatch

但这和您的大致相同。如果您想获得更高的精度，请使用

System.nanoTime()

另请参阅以下问题：

Java时间测量开销

使用番石榴的Stopwatch课程。

测量经过时间的对象（以纳秒为单位）。使用此类而不是直接调用来测量经过时间非常有用 System.nanoTime()出于某些原因，：

• 出于测试或性能方面的原因，可以替换备用时间源。
• 如nanoTime所记录，返回的值没有绝对含义，并且只能解释为相对于nanoTime在不同时间返回的另一个时间戳。秒表是一种更有效的抽象方法，因为它仅公开这些相对值，而不公开绝对值。

Stopwatch stopwatch = Stopwatch.createStarted();
doSomething();
stopwatch.stop(); // optional

long millis = stopwatch.elapsed(TimeUnit.MILLISECONDS);

log.info("that took: " + stopwatch); // formatted string like "12.3 ms"

现在，您可以尝试执行以下操作：

Instant starts = Instant.now();
Thread.sleep(10);
Instant ends = Instant.now();
System.out.println(Duration.between(starts, ends));

输出为ISO 8601。

Spring提供了一个优雅的org.springframework.util.StopWatchClass（s​​pring-core模块）。

StopWatch stopWatch = new StopWatch();
stopWatch.start();
     // Do something
stopWatch.stop();
     System.out.println(stopWatch.getTotalTimeMillis());

使用System.currentTimeMillis()获得的开始时间和结束时间，并计算差值。

class TimeTest1 {
  public static void main(String[] args) {

    long startTime = System.currentTimeMillis();

    long total = 0;
    for (int i = 0; i < 10000000; i++) {
      total += i;
    }

    long stopTime = System.currentTimeMillis();
    long elapsedTime = stopTime - startTime;
    System.out.println(elapsedTime);
  }
} 

本教程的更多信息

代码无效，因为in中的经过变量getElapsedTimeSecs()不是a float或double。

没有内置的秒表实用程序，但是从JSR-310（Java 8 Time）开始，您可以轻松地做到这一点。

ZonedDateTime now = ZonedDateTime.now();
// Do stuff
long seconds = now.until(ZonedDateTime.now(), ChronoUnit.SECONDS);

我没有对此进行基准测试，但是我猜想使用番石榴的秒表会更有效。

试试这个http://introcs.cs.princeton.edu/java/stdlib/Stopwatch.java.html

那很容易

Stopwatch st = new Stopwatch();
// Do smth. here
double time = st.elapsedTime(); // the result in millis

此类是stdlib.jar的一部分

简单易用的秒表类：

import java.time.Duration;
import java.time.Instant;

public class StopWatch {

    Instant startTime, endTime;
    Duration duration;
    boolean isRunning = false;

    public void start() {
        if (isRunning) {
            throw new RuntimeException("Stopwatch is already running.");
        }
        this.isRunning = true;
        startTime = Instant.now();
    }

    public Duration stop() {
        this.endTime = Instant.now();
        if (!isRunning) {
            throw new RuntimeException("Stopwatch has not been started yet");
        }
        isRunning = false;
        Duration result = Duration.between(startTime, endTime);
        if (this.duration == null) {
            this.duration = result;
        } else {
            this.duration = duration.plus(result);
        }

        return this.getElapsedTime();
    }

    public Duration getElapsedTime() {
        return this.duration;
    }

    public void reset() {
        if (this.isRunning) {
            this.stop();
        }
        this.duration = null;
    }
}

用法：

StopWatch sw = new StopWatch();
sw.start();
    // doWork()
sw.stop();
System.out.println( sw.getElapsedTime().toMillis() + "ms");

使用：com.google.common.base.Stopwatch，它简单易用。

<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>23.0</version>
</dependency>

例：

Stopwatch stopwatch = new Stopwatch();
stopwatch.start();

"Do something"

logger.debug("this task took " + stopwatch.stop().elapsedTime(TimeUnit.MILLISECONDS) + " mills");

这个任务花了112磨

试试这个

import java.awt.event.*;

import java.awt.*;

import javax.swing.*;

public class millis extends JFrame implements ActionListener, Runnable
    {

     private long startTime;
     private final static java.text.SimpleDateFormat timerFormat = new java.text.SimpleDateFormat("mm : ss.SSS");
     private final JButton startStopButton= new JButton("Start/stop");
     private Thread updater;
     private boolean isRunning= false;
     private final Runnable displayUpdater= new Runnable()
         {
         public void run()
             {
             displayElapsedTime(System.currentTimeMillis() - millis.this.startTime);
         }
     };
     public void actionPerformed(ActionEvent ae)
         {
         if(isRunning)
             {
             long elapsed= System.currentTimeMillis() - startTime;
             isRunning= false;
             try
                 {
                 updater.join();
                 // Wait for updater to finish
             }
             catch(InterruptedException ie) {}
             displayElapsedTime(elapsed);
             // Display the end-result
         }
         else
             {
             startTime= System.currentTimeMillis();
             isRunning= true;
             updater= new Thread(this);
             updater.start();
         }
     }
     private void displayElapsedTime(long elapsedTime)
         {
         startStopButton.setText(timerFormat.format(new java.util.Date(elapsedTime)));
     }
     public void run()
         {
         try
             {
             while(isRunning)
                 {
                 SwingUtilities.invokeAndWait(displayUpdater);
                 Thread.sleep(50);
             }
         }
         catch(java.lang.reflect.InvocationTargetException ite)
             {
             ite.printStackTrace(System.err);
             // Should never happen!
         }
         catch(InterruptedException ie) {}
         // Ignore and return!
     }
     public millis()
         {
         startStopButton.addActionListener(this);
         getContentPane().add(startStopButton);
         setSize(100,50);
         setVisible(true);
     }
     public static void main(String[] arg)
         {
         new Stopwatch().addWindowListener(new WindowAdapter()
             {
             public void windowClosing(WindowEvent e)
                 {
                 System.exit(0);
             }
         });
         millis s=new millis();
         s.run();
     }
}

试试这个：

/*
 * calculates elapsed time in the form hrs:mins:secs
 */
public class StopWatch
{ 
    private Date startTime;

    public void startTiming()
    {
        startTime = new Date();
    }

    public String stopTiming()
    {
        Date stopTime = new Date();
        long timediff = (stopTime.getTime() - startTime.getTime())/1000L;
        return(DateUtils.formatElapsedTime(timediff));
    }

}

用：

StopWatch sw = new StopWatch();
...
sw.startTiming();
...
String interval = sw.stopTiming();

试试这个。

public class StopWatch { 

      private long startTime = 0;
      private long stopTime = 0;

      public StopWatch()
      {
            startTime = System.currentTimeMillis();
      }

      public void start() {
        startTime = System.currentTimeMillis();
      }

      public void stop() {
        stopTime = System.currentTimeMillis();
        System.out.println("StopWatch: " + getElapsedTime() + " milliseconds.");
        System.out.println("StopWatch: " + getElapsedTimeSecs() + " seconds.");
      }

      /**
       * @param process_name
       */
      public void stop(String process_name) {
            stopTime = System.currentTimeMillis();
            System.out.println(process_name + " StopWatch: " + getElapsedTime() + " milliseconds.");
            System.out.println(process_name + " StopWatch: " + getElapsedTimeSecs() + " seconds.");
      }      

      //elaspsed time in milliseconds
      public long getElapsedTime() {
          return stopTime - startTime;
      }

      //elaspsed time in seconds
      public double getElapsedTimeSecs() {
        double elapsed;
          elapsed = ((double)(stopTime - startTime)) / 1000;
        return elapsed;
      }
} 

用法：

StopWatch watch = new StopWatch();
// do something
watch.stop();

安慰：

StopWatch: 143 milliseconds.
StopWatch: 0.143 seconds.

Performetrics提供了便捷的秒表类，正是您所需要的方式。它可以测量时钟时间以及更多时间：如果需要，它还可以测量CPU时间（用户时间和系统时间）。它小巧，免费，您可以从Maven Central下载。更多信息和示例可以在这里找到：https : //obvj.net/performetrics

Stopwatch sw = new Stopwatch();
sw.start();

// Your code

sw.stop();
sw.printStatistics(System.out);

// Sample output:
// +-----------------+----------------------+--------------+
// | Counter         |         Elapsed time | Time unit    |
// +-----------------+----------------------+--------------+
// | Wall clock time |             85605718 | nanoseconds  |
// | CPU time        |             78000500 | nanoseconds  |
// | User time       |             62400400 | nanoseconds  |
// | System time     |             15600100 | nanoseconds  |
// +-----------------+----------------------+--------------+

您可以将指标转换为任何时间单位（纳秒，毫秒，秒等）。

PS：我是该工具的作者。

您可以在这里找到一个方便的：

https://github.com/varra4u/utils4j/blob/master/src/main/java/com/varra/util/StopWatch.java

用法：

final StopWatch timer = new StopWatch();
System.out.println("Timer: " + timer);
System.out.println("ElapsedTime: " + timer.getElapsedTime());

试试这个。

Java秒表完全可用的解决方案

在这里，您将获得完整的解决方案。

上面链接的解决方案中的一小段：

您可以像下面的代码一样创建一个类，并在代码部分之前和之后使用此类的start和stop方法，以测量所需的时间。

public class Stopwatch{
  private long startTime;
  private long stopTime;

  /**
   starting the stop watch.
  */
  public void start(){
        startTime = System.nanoTime();
  }

  /**
   stopping the stop watch.
  */
  public void stop()
  {     stopTime = System.nanoTime(); }

  /**
  elapsed time in nanoseconds.
  */
  public long time(){
        return (stopTime - startTime);
  }

  public String toString(){
      return "elapsed time: " + time() + " nanoseconds.";
  }

}

谢谢。