Java定时器Timer简述
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2024-03-08 22:41:28
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。...
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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