一种工具,线程用其安排以后在后台线程中执行的任务。可安排任务执行一次,或者定期重复执行。与每个 Timer 对象相对应的是单个后台线程,用于顺序地执行所有计时器任务。计时器任务应该迅速完成。如果完成某个计时器任务的时间太长,那么它会“独占”计时器的任务执行线程。因此,这就可能延迟后续任务的执行,而这些任务就可能“堆在一起”,并且在上述不友好的任务最终完成时才能够被快速连续地执行。
schedule(TimerTask task,long delay) 安排在指定延迟后执行指定的任务。
schedule(TimerTask task,Date time) 安排在指定的时间执行指定的任务。如果此时间已过去,则安排立即执行该任务。
schedule(TimerTask task, long delay, long period) 安排指定的任务从指定的延迟后开始进行重复的固定延迟执行。如果由于任何原因(如垃圾回收或其他后台活动)而延迟了某次执行,则后续执行也将被延迟
schedule(TimerTask task,Date firstTime,long period) 安排指定的任务在指定的时间开始进行重复的固定延迟执行。如果由于任何原因(如垃圾回收或其他后台活动)而延迟了某次执行,则后续执行也将被延迟。
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package test; import java.text.ParseException; import java.text.SimpleDateFormat; import java.util.Date; import java.util.Timer; import java.util.TimerTask; /** * jdk自带定时器 * * @author LIUTIE * */ public class JDKTimer { public static void main(String[] args) throws ParseException { //日期格式工具 final SimpleDateFormat sdf = new SimpleDateFormat( "yyyy-MM-dd HH:mm:ss" ); Timer timer = new Timer(); // 10s后执行定时器,仅执行一次 System.out.print(sdf.format( new Date())); System.out.println( "the timer one will be executed after 10 seconds..." ); long milliseconds = 10 * 1000 ; timer.schedule( new TimerTask() { @Override public void run() { System.out.print(sdf.format( new Date())); System.out.println( "the timer one has finished execution" ); } }, milliseconds); //12秒后执行定时器,每1s执行一次 System.out.print(sdf.format( new Date())); System.out.println( "the timer two will be executed after 12 seconds..." ); //启动后延迟时间 long afterSs = 12 * 1000 ; //执行周期 long intervalSs1 = 1 * 1000 ; timer.schedule( new TimerTask() { // 执行计数器 int i = 0 ; @Override public void run() { System.out.print(sdf.format( new Date())); System.out.println( "the timer two has execution " + (++i) + " timers" ); // 执行10次后关闭定时器 if (i == 10 ) { this .cancel(); } } }, afterSs, intervalSs1); // 指定时间执行定时器,仅执行一次 System.out.print(sdf.format( new Date())); System.out.println( "the timer three will be executed at 2017-06-27 21:47:00..." ); Date date = sdf.parse( "2017-06-27 21:47:00" ); timer.schedule( new TimerTask() { @Override public void run() { System.out.print(sdf.format( new Date())); System.out.println( "the timer three has finished execution" ); } }, date); // 从指定时间开始周期性执行 System.out.print(sdf.format( new Date())); System.out.println( "the timer four will be executed at 2017-06-27 21:48:00..." ); // 执行间隔周期 long intervalSs = 1 * 1000 ; // 开始执行时间 Date beginTime = sdf.parse( "2017-06-27 21:48:00" ); timer.schedule( new TimerTask() { // 执行计数器 int i = 0 ; @Override public void run() { System.out.print(sdf.format( new Date())); System.out.println( "the timer four has execution " + (++i) + " timers" ); // 执行10次后关闭定时器 if (i == 10 ) { this .cancel(); } } }, beginTime, intervalSs); } } |
执行结果
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2017 - 06 - 27 21 : 46 :24the timer one will be executed after 10 seconds... 2017 - 06 - 27 21 : 46 :24the timer two will be executed after 12 seconds... 2017 - 06 - 27 21 : 46 :24the timer three will be executed at 2017 - 06 - 27 21 : 47 : 00 ... 2017 - 06 - 27 21 : 46 :24the timer four will be executed at 2017 - 06 - 27 21 : 48 : 00 ... 2017 - 06 - 27 21 : 46 :34the timer one has finished execution 2017 - 06 - 27 21 : 46 :36the timer two has execution 1 timers 2017 - 06 - 27 21 : 46 :37the timer two has execution 2 timers 2017 - 06 - 27 21 : 46 :38the timer two has execution 3 timers 2017 - 06 - 27 21 : 46 :39the timer two has execution 4 timers 2017 - 06 - 27 21 : 46 :40the timer two has execution 5 timers 2017 - 06 - 27 21 : 46 :41the timer two has execution 6 timers 2017 - 06 - 27 21 : 46 :42the timer two has execution 7 timers 2017 - 06 - 27 21 : 46 :43the timer two has execution 8 timers 2017 - 06 - 27 21 : 46 :44the timer two has execution 9 timers 2017 - 06 - 27 21 : 46 :45the timer two has execution 10 timers 2017 - 06 - 27 21 : 47 :00the timer three has finished execution 2017 - 06 - 27 21 : 48 :00the timer four has execution 1 timers 2017 - 06 - 27 21 : 48 :01the timer four has execution 2 timers 2017 - 06 - 27 21 : 48 :02the timer four has execution 3 timers 2017 - 06 - 27 21 : 48 :03the timer four has execution 4 timers 2017 - 06 - 27 21 : 48 :04the timer four has execution 5 timers 2017 - 06 - 27 21 : 48 :05the timer four has execution 6 timers 2017 - 06 - 27 21 : 48 :06the timer four has execution 7 timers 2017 - 06 - 27 21 : 48 :07the timer four has execution 8 timers 2017 - 06 - 27 21 : 48 :08the timer four has execution 9 timers 2017 - 06 - 27 21 : 48 :09the timer four has execution 10 timers |
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