Question

尝试将函数循环一段特定的时间，请记住该函数大约需要20秒才能完成执行。

显然可以选择使用以下内容：

long startTime = System.currentTimeMillis();
long length = 30000;
while(System.currentTimeMillis() - startTime <= length){
  foo(); // takes 20 seconds to finish executing
}

唯一的缺点就是，如果foo需要20秒才能运行，此代码将不会在30中断，并且在错误之前将循环另外20秒，因此执行40秒。

foo就是这段代码：

new SequenceStrategy(NUMBER_FAIRY_LIGHTS, colours).runLightsAlgorithm();

public class SequenceStrategy implements LightsStrategy {
    private List<Light> fairyLightsList = new ArrayList<>();

    public SequenceStrategy(int numFairyLights, String[] colours) {
        for (int i = 0; i < numFairyLights; i += colours.length) {
            for (int j = 0; j < colours.length && i + j < numFairyLights; j++) {
                fairyLightsList.add(new Light(colours[j], OFF_STATUS, i + j));
            }
        }
    }

    public void runLightsAlgorithm() {
        for (int i = 0; i < fairyLightsList.size(); i++) {
            lightUtilsObject.outputLightMessage(fairyLightsList.get(i).getLightIndex() + 1, fairyLightsList.get(i).getLightColour(), ON_STATUS);
            //Thread sleep for 0.5 second after toggling light in sequence
            lightUtilsObject.lightToggleWait(500);
            lightUtilsObject.outputLightMessage(i + 1, fairyLightsList.get(i).getLightColour(), OFF_STATUS);
            lightUtilsObject.lightToggleWait(500);
        }
    }

}

Answer 1

使用java Timer。

下面是一个简单的演示，其功能需要20秒才能完成，但由于定时器限制为30秒，它会在第二次运行时取消执行。

package javaPractice;

import java.util.Date;
import java.util.Timer;
import java.util.TimerTask;

public class MyTimerTask extends TimerTask {

    @Override
    public void run() {
        System.out.println("Timer task started at:"+new Date());
        completeTask();
        System.out.println("Timer task finished at:"+new Date());
    }

    private void completeTask() {
        try {
            //assuming it takes 20 secs to complete the task
            Thread.sleep(20000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    public static void main(String args[]){
        TimerTask timerTask = new MyTimerTask();
        //running timer task as daemon thread
        Timer timer = new Timer(true);
        timer.scheduleAtFixedRate(timerTask, 0, 10*1000);
        System.out.println("TimerTask started");
        //cancel after sometime
        try {
            Thread.sleep(30000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        timer.cancel();
        System.out.println("TimerTask cancelled");
        try {
            Thread.sleep(3000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("Done");
    }

}

Refrence

如何将函数循环一段时间

1 个答案: