Timer和ScheduledExecutorService区别

Timer特点：

 

1、一个Timer只占用一个线程

timer有多个timerTask的情况，如果一个timerTask有执行时间过长，其它的timerTask就会被耽误

2、如果TimerTask抛出未检查的异常，Timer会由于该异常导致中断。后续的TimerTask任务也不会执行

示例：

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

 public class TimerTest extends TimerTask {

         private String jobName = "" ;

         public TimerTest(String jobName) {
                super();
                this.jobName = jobName;
        }

         int count = 0;

         @Override
         public void run() {
               System. out.println(jobName + " " + new Date() + " beep " + (++count));
                try {
                       if (jobName .equals("job1" )) {
                            Thread. sleep(1000);
                             throw new RuntimeException();
                      }

               } catch (InterruptedException e) {
                       // TODO Auto-generated catch block
                      e.printStackTrace();
               }
        }

         public static void main(String[] args) {
               Timer timer = new Timer();
                long period = 2000;
                // 从现在开始 1 秒钟之后，每隔 2秒钟执行一次 job1
               timer.schedule( new TimerTest("job1" ), 0, period);
                // 每隔 2 秒钟执行一次 job2
               timer.schedule( new TimerTest("job2" ), 0, period);
        }
 }
 执行结果
 job1 Tue Apr 08 23:37:17 CST 2014 beep 1
 Exception in thread "Timer-0" java.lang.RuntimeException
        at TimerTest.run( TimerTest.java:20)
        at java.util.TimerThread.mainLoop( Timer.java:512)
        at java.util.TimerThread.run( Timer.java:462)

ScheduledExecutorService(实现类ScheduledThreadPoolExecutor)特点：

1、ScheduledExecutorService是多线程

只要线程池不设置为1，每个线程任务都能按照各自的频率执行。

2、如果线程任务抛出未检查的异常，ScheduledExecutorService只是中断该线程任务，其它任务正常执行

示例：

 import static java.util.concurrent.TimeUnit.SECONDS;
 import java.util.Date;
 import java.util.TimerTask;
 import java.util.concurrent.Executors;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.ScheduledFuture;

 public class TestScheduledThread extends TimerTask {

         private String jobName = "" ;

         public TestScheduledThread(String jobName) {
                super();
                this.jobName = jobName;
        }

         int count = 0;

         @Override
         public void run() {
               System. out.println(jobName + " " + new Date() + " beep " + (++count));
                try {
                       if (jobName .equals("job1" )) {
                            Thread. sleep(1000);
                             throw new RuntimeException();
                      }

               } catch (InterruptedException e) {
                       // TODO Auto-generated catch block
                      e.printStackTrace();
               }
        }

         public static void main(String[] args) {
                final ScheduledExecutorService scheduler = Executors
                            . newScheduledThreadPool(2);
                //每隔2秒运行一次
                final ScheduledFuture beeperHandle = scheduler.scheduleAtFixedRate(
                             new TimerTest("job1" ), 0, 2, SECONDS);
                //每隔2秒运行一次
                final ScheduledFuture beeperHandle2 = scheduler.scheduleAtFixedRate(
                             new TimerTest("job2" ), 0, 2, SECONDS);
        }
 }

 

执行结果：

job2 Tue Apr 08 23:42:58 CST 2014 beep 1

job1 Tue Apr 08 23:42:58 CST 2014 beep 1

job2 Tue Apr 08 23:43:00 CST 2014 beep 2

job2 Tue Apr 08 23:43:02 CST 2014 beep 3

job2 Tue Apr 08 23:43:04 CST 2014 beep 4

job2 Tue Apr 08 23:43:06 CST 2014 beep 5

job2 Tue Apr 08 23:43:08 CST 2014 beep 6