由 dawei
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 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,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,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,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,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