ScheduledExecutorService 定时器用法

1，如果只是想简单的写个定时任务，比如10分钟跑一次，那么ScheduledExecutorService是比较方便的，下面举个简单的例子

import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class CrawlerRun {
   private static final Logger logger = LoggerFactory.getLogger(CrawlerRun.class);
   public static void main(String[] args) {
      ScheduledExecutorService service = Executors.newScheduledThreadPool(8);//先定义8个线程空间
      final ScheduledFuture<?> future = service.scheduleAtFixedRate(new CrawlerTest(), 0,10,
                 TimeUnit.MINUTES);//CrawlerTest()是一个实现Runnable接口的类，会自动运行里面的run()方法，0的意思就是启动等待时间，这里就是直接运行，
                                 10是10分钟，要是想小时，就把TimeUnit.MINUTES换成 TimeUnit.HOURS

      //使用1个线程
         Thread t= new Thread(new Runnable() {
                public void run() {
                    try {
                        future.get();
                    } catch (Exception e) {
                        logger.error(e.getCause().getMessage(), e.getCause());//日志信息输出
                        future.cancel(false);//关闭线程
                    }
                }
        });
        t.start() ;

   }
}

2，如果想早上8点到晚上8点采集（期间还是10分钟跑一次），别的时间不采集，那就要在CrawlerTest()里面run()方法做判断

import java.util.Calendar;

public void run() {
        try {
            Calendar ca=Calendar.getInstance();
            int hour = ca.get(Calendar.HOUR_OF_DAY) ;//获取当时时间数
            if(hour <8 || hour >20) return ;
            this.Crawler2();
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

3，如果想指定就8点，12点，16点，20点采集，别的时间都不采集，那就要加判断

import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class CrawlerRun {
   private static final Logger logger = LoggerFactory.getLogger(CrawlerRun.class);

   private static long delayTime(long currentTime , String campareDateStr) {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        Date date = new Date() ; 

        String str = TimeFormat.getYearMonthDate();
        str = str.replaceAll("00:00:00", campareDateStr) ;
        try {
            date = sdf.parse(str) ;
        } catch (ParseException e1) {
            e1.printStackTrace();
        }
        long dateMillis = date.getTime() ;

        return dateMillis - currentTime ;

    }
   public static void main(String[] args) {
        long currentTime = System.currentTimeMillis() ;
        long realDelayTime = 0 ;
        long delayTime = CrawlerRun.delayTime(currentTime, "08:00:00") ;
        long delayTime2= CrawlerRun.delayTime(currentTime, "12:00:00") ;
        long delayTime3= CrawlerRun.delayTime(currentTime, "16:00:00") ;
        long delayTime4= CrawlerRun.delayTime(currentTime, "20:00:00") ;

        List<Long> list = new ArrayList<Long>() ;

        list.add(delayTime) ;
        list.add(delayTime2) ;
        list.add(delayTime3) ;
        list.add(delayTime4) ;

        Collections.sort(list);

        for (Long time : list) {
            if(time < 0 ) continue ;
            else{
                realDelayTime = time;
                break;
                }
        }

      ScheduledExecutorService service = Executors.newScheduledThreadPool(8);//先定义8个线程空间
     final ScheduledFuture<?> future = service.scheduleAtFixedRate(new CrawlerTest(), realDelayTime/1000, 4*60*60,
                 TimeUnit.SECONDS);

      //使用1个线程
         Thread t= new Thread(new Runnable() {
                public void run() {
                    try {
                        future.get();
                    } catch (Exception e) {
                        logger.error(e.getCause().getMessage(), e.getCause());//日志信息输出
                        future.cancel(false);//关闭线程
                    }
                }
        });
        t.start() ;

   }
}