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Java定时器Timer简述

2019年07月22日 | 移动技术网IT编程 | 我要评论

概述

主要用于java线程里指定时间或周期运行任务。timer是线程安全的，但不提供实时性(real-time)保证。

构造函数

timer()

默认构造函数。

timer(boolean)

指定关联线程是否作为daemon线程。

timer(string)

指定关联线程的名称。

timer(string, boolean)

同时指定关联线程的名称和是否作为daemon。

schdule方法

schedule(timertask task, long delay)

以当前时间为基准，延迟指定的毫秒后执行一次timertask任务。

schedule(timertask task, date time)

在指定的日期执行一次timertask任务。

如果日期time早于当前时间，则立刻执行。

使用示例

public class demo {
 private static timer timer = new timer();
 public static class mytask extends timertask {
 @override
 public void run() {
  system.out.println("run time：" + new date().tostring());
 }
 }
 public static void main(string[] args) {
 try {
  mytask task = new mytask();
  simpledateformat sdf = new simpledateformat("yyyy-mm-dd hh:mm:ss");
  string datestr = "2016-12-27 14:36:00";
  date date = sdf.parse(datestr);
  system.out.println("date = " + date.tostring() + " nowtime = " + new date().tostring());
  timer.schedule(task, date);
 } catch (parseexception e) {
  e.printstacktrace();
 }
 }
}

执行结果

date = tue dec 27 14:36:00 cst 2016 nowtime = tue dec 27 21:28:04 cst 2016
run time：tue dec 27 21:28:04 cst 2016

说明是立刻执行。

schedule(timertask task, long delay, long period)

以当前时间为基准，延迟指定的毫秒后，再按指定的时间间隔地无限次数的执行timertask任务。(fixed-delay execution)

使用示例

public class demo {
 private static timer timer = new timer();
 public static class mytask extends timertask {
 @override
 public void run() {
  system.out.println("run time: " + new date().tostring());
 }
 }
 public static void main(string[] args) {
 mytask task = new mytask();
 system.out.println("now time: " + new date().tostring());
 timer.schedule(task, 3000, 5000);
 }
}

执行结果

now time: tue dec 27 21:34:59 cst 2016
run time: tue dec 27 21:35:02 cst 2016
run time: tue dec 27 21:35:07 cst 2016
run time: tue dec 27 21:35:12 cst 2016
run time: tue dec 27 21:35:17 cst 2016

说明以当前基准时间延迟3秒后执行一次，以后按指定间隔时间5秒无限次数的执行。

schedule(timertask task, date firsttime, long period)

在指定的日期之后，按指定的时间间隔地无限次数的执行timertask任务。(fixed-delay execution)

如果日期firsttime早于当前时间，则立刻执行，且不执行在时间差内的任务。

使用示例

public class demo {
 private static timer timer = new timer();
 public static class mytask extends timertask {
 @override
 public void run() {
  system.out.println("run time：" + new date().tostring());
 }
 public static void main(string[] args) {
  try {
  mytask task = new mytask();
  simpledateformat sdf = new simpledateformat("yyyy-mm-dd hh:mm:ss");
  string datestr = "2016-12-27 14:36:00";
  date date = sdf.parse(datestr);
  system.out.println("date = " + date.tostring() + " nowtime = " + new date().tostring());
  timer.schedule(task, date, 3000);
  } catch (parseexception e) {
  e.printstacktrace();
  }
 }
 }
}

执行结果

date = tue dec 27 14:36:00 cst 2016 nowtime = tue dec 27 21:43:30 cst 2016
run time：tue dec 27 21:43:30 cst 2016
run time：tue dec 27 21:43:33 cst 2016
run time：tue dec 27 21:43:36 cst 2016

说明指定的之间早于当前时间，则立刻执行，不会补充时间差内的任务。

scheduleatfixedrate方法

scheduleatfixedrate(timertask task, long delay, long period)

以当前时间为基准，延迟指定的毫秒后，再按指定的时间间隔周期性地无限次数的执行timertask任务。(fixed-rate execution)

使用示例

public class demo {
 private static timer timer = new timer();
 public static class mytask extends timertask {
 @override
 public void run() {
  system.out.println("run time: " + new date().tostring());
 }
 }
 public static void main(string[] args) {
 mytask task = new mytask();
 system.out.println("now time: " + new date().tostring());
 timer.scheduleatfixedrate(task, 3000, 5000);
 }
}

执行结果

now time: tue dec 27 21:58:03 cst 2016
run time: tue dec 27 21:58:06 cst 2016
run time: tue dec 27 21:58:11 cst 2016
run time: tue dec 27 21:58:16 cst 2016
run time: tue dec 27 21:58:21 cst 2016

说明以当前基准时间延迟3秒后执行一次，以后按指定间隔时间5秒无限次数的执行。

scheduleatfixedrate(timertask task, date firsttime, long period)

在指定的日期之后，按指定的时间间隔周期性地无限次数的执行timertask任务。(fixed-rate execution)

如果日期firsttime早于当前时间，则立即执行，并补充性的执行在时间差内的任务。

使用示例

public class demo {
 private static timer timer = new timer();
 public static class mytask extends timertask {
 @override
 public void run() {
  system.out.println("run time：" + new date().tostring());
 }
 public static void main(string[] args) {
  try {
  mytask task = new mytask();
  simpledateformat sdf = new simpledateformat("yyyy-mm-dd hh:mm:ss");
  string datestr = "2016-12-27 22:02:00";
  date date = sdf.parse(datestr);
  system.out.println("date = " + date.tostring() + " nowtime = " + new date().tostring());
  timer.scheduleatfixedrate(task, date, 5000);
  } catch (parseexception e) {
  e.printstacktrace();
  }
 }
 }
}

执行结果

date = tue dec 27 22:02:00 cst 2016 nowtime = tue dec 27 22:02:54 cst 2016
run time：tue dec 27 22:02:54 cst 2016
run time：tue dec 27 22:02:54 cst 2016
run time：tue dec 27 22:02:54 cst 2016
run time：tue dec 27 22:02:54 cst 2016
run time：tue dec 27 22:02:54 cst 2016
run time：tue dec 27 22:02:54 cst 2016
run time：tue dec 27 22:02:54 cst 2016
run time：tue dec 27 22:02:54 cst 2016
run time：tue dec 27 22:02:54 cst 2016
run time：tue dec 27 22:02:54 cst 2016
run time：tue dec 27 22:02:54 cst 2016
run time：tue dec 27 22:02:55 cst 2016
run time：tue dec 27 22:03:00 cst 2016
run time：tue dec 27 22:03:05 cst 2016

说明指定的之间早于当前时间，则立刻执行。

在时间22:02:00--22:02:54内大约有11个5秒间隔，则优先补充性的执行在时间差内的任务，然后在22:02:55补充完毕(执行12次。ps：0-55秒区间段内首位都算上，正好触发12次)，此后每隔5秒执行一次定时任务。

执行任务延时对比之 schedule 和 scheduleatfixedrate

schedule不延时

使用示例

public class demo {
 private static timer timer = new timer();
 private static int runcount = 0;
 public static class mytask extends timertask {
 @override
 public void run() {
  try {
  system.out.println("begin run time: " + new date().tostring());
  thread.sleep(3000);
  system.out.println("end run time: " + new date().tostring());
  runcount++;
  if (runcount == 3) {
   timer.cancel();
  }
  } catch (interruptedexception e) {
  e.printstacktrace();
  }
 }
 }
 public static void main(string[] args) {
 try {
  mytask task = new mytask();
  simpledateformat sdf = new simpledateformat("yyyy-mm-dd hh:mm:ss");
  string datestr = "2016-12-27 14:36:00";
  date date = sdf.parse(datestr);
  system.out.println("date = " + date.tostring() + " nowtime = " + new date().tostring());
  timer.schedule(task, date, 5000);
 } catch (parseexception e) {
  e.printstacktrace();
 }
 }
}

执行结果

早于当前基准时间

date = tue dec 27 14:36:00 cst 2016 nowtime = tue dec 27 22:23:37 cst 2016
begin run time: tue dec 27 22:23:37 cst 2016
end run time: tue dec 27 22:23:40 cst 2016
begin run time: tue dec 27 22:23:42 cst 2016
end run time: tue dec 27 22:23:45 cst 2016
begin run time: tue dec 27 22:23:47 cst 2016
end run time: tue dec 27 22:23:50 cst 2016

process finished with exit code 0

晚于当前基准时间

date = tue dec 27 22:42:00 cst 2016 nowtime = tue dec 27 22:41:54 cst 2016
begin run time: tue dec 27 22:42:00 cst 2016
end run time: tue dec 27 22:42:03 cst 2016
begin run time: tue dec 27 22:42:05 cst 2016
end run time: tue dec 27 22:42:08 cst 2016
begin run time: tue dec 27 22:42:10 cst 2016
end run time: tue dec 27 22:42:13 cst 2016

process finished with exit code 0

不管早还是晚于基准时间，都不进行补偿，下一次任务的执行时间参考的是上一次任务的开始时间点来计算。

schedule延时

使用示例

public class demo {
 private static timer timer = new timer();
 private static int runcount = 0;
 public static class mytask extends timertask {
 @override
 public void run() {
  try {
  system.out.println("begin run time: " + new date().tostring());
  thread.sleep(5000);
  system.out.println("end run time: " + new date().tostring());
  runcount++;
  if (runcount == 3) {
   timer.cancel();
  }
  } catch (interruptedexception e) {
  e.printstacktrace();
  }
 }
 }
 public static void main(string[] args) {
 try {
  mytask task = new mytask();
  simpledateformat sdf = new simpledateformat("yyyy-mm-dd hh:mm:ss");
  string datestr = "2016-12-27 22:42:00";
  date date = sdf.parse(datestr);
  system.out.println("date = " + date.tostring() + " nowtime = " + new date().tostring());
  timer.schedule(task, date, 3000);
 } catch (parseexception e) {
  e.printstacktrace();
 }
 }
}

执行结果

早于当前基准时间

date = tue dec 27 22:42:00 cst 2016 nowtime = tue dec 27 22:45:17 cst 2016
begin run time: tue dec 27 22:45:17 cst 2016
end run time: tue dec 27 22:45:22 cst 2016
begin run time: tue dec 27 22:45:22 cst 2016
end run time: tue dec 27 22:45:27 cst 2016
begin run time: tue dec 27 22:45:27 cst 2016
end run time: tue dec 27 22:45:32 cst 2016

process finished with exit code 0

晚于当前基准时间

date = tue dec 27 22:47:00 cst 2016 nowtime = tue dec 27 22:46:27 cst 2016
begin run time: tue dec 27 22:47:00 cst 2016
end run time: tue dec 27 22:47:05 cst 2016
begin run time: tue dec 27 22:47:05 cst 2016
end run time: tue dec 27 22:47:10 cst 2016
begin run time: tue dec 27 22:47:10 cst 2016
end run time: tue dec 27 22:47:15 cst 2016

process finished with exit code 0

不管早还是晚于当前基准时间，都不进行补偿，下一次任务的执行时间都是参考上一次任务结束的时间点来计算。

scheduleatfixedrate不延时

使用示例

public class demo {
 private static timer timer = new timer();
 private static int runcount = 0;
 public static class mytask extends timertask {
 @override
 public void run() {
  try {
  system.out.println("begin run time: " + new date().tostring());
  thread.sleep(3000);
  system.out.println("end run time: " + new date().tostring());
  runcount++;
  if (runcount == 1000) {
   timer.cancel();
  }
  } catch (interruptedexception e) {
  e.printstacktrace();
  }
 }
 }
 public static void main(string[] args) {
 try {
  mytask task = new mytask();
  simpledateformat sdf = new simpledateformat("yyyy-mm-dd hh:mm:ss");
  string datestr = "2016-12-27 22:51:42";
  date date = sdf.parse(datestr);
  system.out.println("date = " + date.tostring() + " nowtime = " + new date().tostring());
  timer.scheduleatfixedrate(task, date, 5000);
 } catch (parseexception e) {
  e.printstacktrace();
 }
 }
}

执行结果

早于当前基准时间

date = tue dec 27 22:51:42 cst 2016 nowtime = tue dec 27 22:51:57 cst 2016
begin run time: tue dec 27 22:51:57 cst 2016
end run time: tue dec 27 22:52:00 cst 2016
begin run time: tue dec 27 22:52:00 cst 2016
end run time: tue dec 27 22:52:03 cst 2016
begin run time: tue dec 27 22:52:03 cst 2016
end run time: tue dec 27 22:52:06 cst 2016
begin run time: tue dec 27 22:52:06 cst 2016
end run time: tue dec 27 22:52:09 cst 2016
begin run time: tue dec 27 22:52:09 cst 2016
end run time: tue dec 27 22:52:12 cst 2016
begin run time: tue dec 27 22:52:12 cst 2016
end run time: tue dec 27 22:52:15 cst 2016
begin run time: tue dec 27 22:52:15 cst 2016
end run time: tue dec 27 22:52:18 cst 2016
begin run time: tue dec 27 22:52:18 cst 2016
end run time: tue dec 27 22:52:21 cst 2016
begin run time: tue dec 27 22:52:22 cst 2016
end run time: tue dec 27 22:52:25 cst 2016
begin run time: tue dec 27 22:52:27 cst 2016
end run time: tue dec 27 22:52:30 cst 2016
begin run time: tue dec 27 22:52:32 cst 2016
end run time: tue dec 27 22:52:35 cst 2016
begin run time: tue dec 27 22:52:37 cst 2016
end run time: tue dec 27 22:52:40 cst 2016
begin run time: tue dec 27 22:52:42 cst 2016
end run time: tue dec 27 22:52:45 cst 2016
begin run time: tue dec 27 22:52:47 cst 2016
end run time: tue dec 27 22:52:50 cst 2016
begin run time: tue dec 27 22:52:52 cst 2016
end run time: tue dec 27 22:52:55 cst 2016
begin run time: tue dec 27 22:52:57 cst 2016
end run time: tue dec 27 22:53:00 cst 2016

process finished with exit code 0

晚于当前基准时间

date = tue dec 27 22:37:00 cst 2016 nowtime = tue dec 27 22:36:06 cst 2016
begin run time: tue dec 27 22:37:00 cst 2016
end run time: tue dec 27 22:37:03 cst 2016
begin run time: tue dec 27 22:37:05 cst 2016
end run time: tue dec 27 22:37:08 cst 2016
begin run time: tue dec 27 22:37:10 cst 2016
end run time: tue dec 27 22:37:13 cst 2016

process finished with exit code 0

不延时的情况下，当早于基准时间时，时间差内的执行任务未补偿完时，下一次执行任务的时间参考的是上一次执行任务的结束时间；一旦补偿完毕（注意粗体时间点），下一次执行任务的时间参考的是上一次执行任务的开始时间；当晚于基准时间时，下一次执行任务的时间参考的是上一次执行任务的开始时间。

scheduleatfixedrate延时

使用示例

public class demo {
 private static timer timer = new timer();
 private static int runcount = 0;
 public static class mytask extends timertask {
 @override
 public void run() {
  try {
  system.out.println("begin run time: " + new date().tostring());
  thread.sleep(5000);
  system.out.println("end run time: " + new date().tostring());
  runcount++;
  if (runcount == 3) {
   timer.cancel();
  }
  } catch (interruptedexception e) {
  e.printstacktrace();
  }
 }
 }
 public static void main(string[] args) {
 try {
  mytask task = new mytask();
  simpledateformat sdf = new simpledateformat("yyyy-mm-dd hh:mm:ss");
  string datestr = "2016-12-27 22:28:00";
  date date = sdf.parse(datestr);
  system.out.println("date = " + date.tostring() + " nowtime = " + new date().tostring());
  timer.scheduleatfixedrate(task, date, 3000);
 } catch (parseexception e) {
  e.printstacktrace();
 }
 }
}

执行结果

早于当前基准时间

date = tue dec 27 23:01:00 cst 2016 nowtime = tue dec 27 23:01:19 cst 2016
begin run time: tue dec 27 23:01:19 cst 2016
end run time: tue dec 27 23:01:24 cst 2016
begin run time: tue dec 27 23:01:24 cst 2016
end run time: tue dec 27 23:01:29 cst 2016
begin run time: tue dec 27 23:01:29 cst 2016
end run time: tue dec 27 23:01:34 cst 2016
begin run time: tue dec 27 23:01:34 cst 2016
end run time: tue dec 27 23:01:39 cst 2016

晚于当前基准时间

date = tue dec 27 22:28:00 cst 2016 nowtime = tue dec 27 22:27:55 cst 2016
begin run time: tue dec 27 22:28:00 cst 2016
end run time: tue dec 27 22:28:05 cst 2016
begin run time: tue dec 27 22:28:05 cst 2016
end run time: tue dec 27 22:28:10 cst 2016
begin run time: tue dec 27 22:28:10 cst 2016
end run time: tue dec 27 22:28:15 cst 2016

process finished with exit code 0

延时的情况下，即使是早于基准时间，由于延时效应，根本不可能补偿完毕时间差内的执行任务，故而在延时的情况下，下一次任务的执行时间都是参考上一次任务结束的时间来计算。

对比总结

	执行任务不延时	执行任务延时
早于当前基准时间	schedule：下一次任务的执行时间参考的是上一次任务的开始时间来计算。 scheduleatfixedrate：当早于基准时间时，时间差内的执行任务未补偿完时，下一次执行任务的时间参考的是上一次任务的结束时间；一旦补偿完毕，下一次执行任务的时间参考上一次任务的开始时间来计算。	二者一样。下一次任务的执行时间都是参考上一次任务的结束时间来计算。
晚于当前基准时间	二者一样。下一次任务的执行时间参考的是上一次任务的开始时间来计算。	二者一样。下一次任务的执行时间都是参考上一次任务的结束时间来计算。

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Java定时器Timer简述

2019年07月22日 | 移动技术网IT编程 | 我要评论

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