概述
主要用于Java線程里指定時間或周期運行任務(wù)。Timer是線程安全的，但不提供實時性(real-time)保證。
構(gòu)造函數(shù)
Timer()
默認(rèn)構(gòu)造函數(shù)。
Timer(boolean)
指定關(guān)聯(lián)線程是否作為daemon線程。
Timer(String)
指定關(guān)聯(lián)線程的名稱。
Timer(String, boolean)
同時指定關(guān)聯(lián)線程的名稱和是否作為daemon。
schdule方法
schedule(TimerTask task, long delay)
以當(dāng)前時間為基準(zhǔn)，延遲指定的毫秒后執(zhí)行一次TimerTask任務(wù)。
schedule(TimerTask task, Date time)
在指定的日期執(zhí)行一次TimerTask任務(wù)。
如果日期time早于當(dāng)前時間，則立刻執(zhí)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(); } }}執(zhí)行結(jié)果
Date = Tue Dec 27 14:36:00 CST 2016 NowTime = Tue Dec 27 21:28:04 CST 2016Run Time：Tue Dec 27 21:28:04 CST 2016
說明是立刻執(zhí)行。
schedule(TimerTask task, long delay, long period)
以當(dāng)前時間為基準(zhǔn)，延遲指定的毫秒后，再按指定的時間間隔地?zé)o限次數(shù)的執(zhí)行TimerTask任務(wù)。(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); }}執(zhí)行結(jié)果
Now Time: Tue Dec 27 21:34:59 CST 2016Run Time: Tue Dec 27 21:35:02 CST 2016Run Time: Tue Dec 27 21:35:07 CST 2016Run Time: Tue Dec 27 21:35:12 CST 2016Run Time: Tue Dec 27 21:35:17 CST 2016
說明以當(dāng)前基準(zhǔn)時間延遲3秒后執(zhí)行一次，以后按指定間隔時間5秒無限次數(shù)的執(zhí)行。
schedule(TimerTask task, Date firstTime, long period)
在指定的日期之后，按指定的時間間隔地?zé)o限次數(shù)的執(zhí)行TimerTask任務(wù)。(fixed-delay execution)
如果日期firstTime早于當(dāng)前時間，則立刻執(zhí)行，且不執(zhí)行在時間差內(nèi)的任務(wù)。
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(); } } }}執(zhí)行結(jié)果
Date = Tue Dec 27 14:36:00 CST 2016 NowTime = Tue Dec 27 21:43:30 CST 2016Run Time：Tue Dec 27 21:43:30 CST 2016Run Time：Tue Dec 27 21:43:33 CST 2016Run Time：Tue Dec 27 21:43:36 CST 2016
說明指定的之間早于當(dāng)前時間，則立刻執(zhí)行，不會補充時間差內(nèi)的任務(wù)。
scheduleAtFixedRate方法
scheduleAtFixedRate(TimerTask task, long delay, long period)
以當(dāng)前時間為基準(zhǔn)，延遲指定的毫秒后，再按指定的時間間隔周期性地?zé)o限次數(shù)的執(zhí)行TimerTask任務(wù)。(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); }}執(zhí)行結(jié)果
Now Time: Tue Dec 27 21:58:03 CST 2016Run Time: Tue Dec 27 21:58:06 CST 2016Run Time: Tue Dec 27 21:58:11 CST 2016Run Time: Tue Dec 27 21:58:16 CST 2016Run Time: Tue Dec 27 21:58:21 CST 2016
說明以當(dāng)前基準(zhǔn)時間延遲3秒后執(zhí)行一次，以后按指定間隔時間5秒無限次數(shù)的執(zhí)行。
scheduleAtFixedRate(TimerTask task, Date firstTime, long period)
在指定的日期之后，按指定的時間間隔周期性地?zé)o限次數(shù)的執(zhí)行TimerTask任務(wù)。(fixed-rate execution)
如果日期firstTime早于當(dāng)前時間，則立即執(zhí)行，并補充性的執(zhí)行在時間差內(nèi)的任務(wù)。
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(); } } }}執(zhí)行結(jié)果
Date = Tue Dec 27 22:02:00 CST 2016 NowTime = Tue Dec 27 22:02:54 CST 2016Run Time：Tue Dec 27 22:02:54 CST 2016Run Time：Tue Dec 27 22:02:54 CST 2016Run Time：Tue Dec 27 22:02:54 CST 2016Run Time：Tue Dec 27 22:02:54 CST 2016Run Time：Tue Dec 27 22:02:54 CST 2016Run Time：Tue Dec 27 22:02:54 CST 2016Run Time：Tue Dec 27 22:02:54 CST 2016Run Time：Tue Dec 27 22:02:54 CST 2016Run Time：Tue Dec 27 22:02:54 CST 2016Run Time：Tue Dec 27 22:02:54 CST 2016Run Time：Tue Dec 27 22:02:54 CST 2016Run Time：Tue Dec 27 22:02:55 CST 2016Run Time：Tue Dec 27 22:03:00 CST 2016Run Time：Tue Dec 27 22:03:05 CST 2016
說明指定的之間早于當(dāng)前時間，則立刻執(zhí)行。
在時間22:02:00--22:02:54內(nèi)大約有11個5秒間隔，則優(yōu)先補充性的執(zhí)行在時間差內(nèi)的任務(wù)，然后在22:02:55補充完畢(執(zhí)行12次。ps：0-55秒?yún)^(qū)間段內(nèi)首位都算上，正好觸發(fā)12次)，此后每隔5秒執(zhí)行一次定時任務(wù)。
執(zhí)行任務(wù)延時對比之 schedule 和 scheduleAtFixedRate
schedule不延時
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(); } }}執(zhí)行結(jié)果
早于當(dāng)前基準(zhǔn)時間
Date = Tue Dec 27 14:36:00 CST 2016 NowTime = Tue Dec 27 22:23:37 CST 2016Begin Run Time: Tue Dec 27 22:23:37 CST 2016End Run Time: Tue Dec 27 22:23:40 CST 2016Begin Run Time: Tue Dec 27 22:23:42 CST 2016End Run Time: Tue Dec 27 22:23:45 CST 2016Begin Run Time: Tue Dec 27 22:23:47 CST 2016End Run Time: Tue Dec 27 22:23:50 CST 2016Process finished with exit code 0
晚于當(dāng)前基準(zhǔn)時間
Date = Tue Dec 27 22:42:00 CST 2016 NowTime = Tue Dec 27 22:41:54 CST 2016Begin Run Time: Tue Dec 27 22:42:00 CST 2016End Run Time: Tue Dec 27 22:42:03 CST 2016Begin Run Time: Tue Dec 27 22:42:05 CST 2016End Run Time: Tue Dec 27 22:42:08 CST 2016Begin Run Time: Tue Dec 27 22:42:10 CST 2016End Run Time: Tue Dec 27 22:42:13 CST 2016Process finished with exit code 0
不管早還是晚于基準(zhǔn)時間，都不進行補償，下一次任務(wù)的執(zhí)行時間參考的是上一次任務(wù)的開始時間點來計算。
schedule延時
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(); } }}執(zhí)行結(jié)果
早于當(dāng)前基準(zhǔn)時間
Date = Tue Dec 27 22:42:00 CST 2016 NowTime = Tue Dec 27 22:45:17 CST 2016Begin Run Time: Tue Dec 27 22:45:17 CST 2016End Run Time: Tue Dec 27 22:45:22 CST 2016Begin Run Time: Tue Dec 27 22:45:22 CST 2016End Run Time: Tue Dec 27 22:45:27 CST 2016Begin Run Time: Tue Dec 27 22:45:27 CST 2016End Run Time: Tue Dec 27 22:45:32 CST 2016Process finished with exit code 0
晚于當(dāng)前基準(zhǔn)時間
Date = Tue Dec 27 22:47:00 CST 2016 NowTime = Tue Dec 27 22:46:27 CST 2016Begin Run Time: Tue Dec 27 22:47:00 CST 2016End Run Time: Tue Dec 27 22:47:05 CST 2016Begin Run Time: Tue Dec 27 22:47:05 CST 2016End Run Time: Tue Dec 27 22:47:10 CST 2016Begin Run Time: Tue Dec 27 22:47:10 CST 2016End Run Time: Tue Dec 27 22:47:15 CST 2016Process finished with exit code 0
不管早還是晚于當(dāng)前基準(zhǔn)時間，都不進行補償，下一次任務(wù)的執(zhí)行時間都是參考上一次任務(wù)結(jié)束的時間點來計算。
scheduleAtFixedRate不延時
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(); } }}執(zhí)行結(jié)果
早于當(dāng)前基準(zhǔn)時間
Date = Tue Dec 27 22:51:42 CST 2016 NowTime = Tue Dec 27 22:51:57 CST 2016Begin Run Time: Tue Dec 27 22:51:57 CST 2016End Run Time: Tue Dec 27 22:52:00 CST 2016Begin Run Time: Tue Dec 27 22:52:00 CST 2016End Run Time: Tue Dec 27 22:52:03 CST 2016Begin Run Time: Tue Dec 27 22:52:03 CST 2016End Run Time: Tue Dec 27 22:52:06 CST 2016Begin Run Time: Tue Dec 27 22:52:06 CST 2016End Run Time: Tue Dec 27 22:52:09 CST 2016Begin Run Time: Tue Dec 27 22:52:09 CST 2016End Run Time: Tue Dec 27 22:52:12 CST 2016Begin Run Time: Tue Dec 27 22:52:12 CST 2016End Run Time: Tue Dec 27 22:52:15 CST 2016Begin Run Time: Tue Dec 27 22:52:15 CST 2016End Run Time: Tue Dec 27 22:52:18 CST 2016Begin Run Time: Tue Dec 27 22:52:18 CST 2016End Run Time: Tue Dec 27 22:52:21 CST 2016Begin Run Time: Tue Dec 27 22:52:22 CST 2016End Run Time: Tue Dec 27 22:52:25 CST 2016Begin Run Time: Tue Dec 27 22:52:27 CST 2016End Run Time: Tue Dec 27 22:52:30 CST 2016Begin Run Time: Tue Dec 27 22:52:32 CST 2016End Run Time: Tue Dec 27 22:52:35 CST 2016Begin Run Time: Tue Dec 27 22:52:37 CST 2016End Run Time: Tue Dec 27 22:52:40 CST 2016Begin Run Time: Tue Dec 27 22:52:42 CST 2016End Run Time: Tue Dec 27 22:52:45 CST 2016Begin Run Time: Tue Dec 27 22:52:47 CST 2016End Run Time: Tue Dec 27 22:52:50 CST 2016Begin Run Time: Tue Dec 27 22:52:52 CST 2016End Run Time: Tue Dec 27 22:52:55 CST 2016Begin Run Time: Tue Dec 27 22:52:57 CST 2016End Run Time: Tue Dec 27 22:53:00 CST 2016Process finished with exit code 0
晚于當(dāng)前基準(zhǔn)時間
Date = Tue Dec 27 22:37:00 CST 2016 NowTime = Tue Dec 27 22:36:06 CST 2016Begin Run Time: Tue Dec 27 22:37:00 CST 2016End Run Time: Tue Dec 27 22:37:03 CST 2016Begin Run Time: Tue Dec 27 22:37:05 CST 2016End Run Time: Tue Dec 27 22:37:08 CST 2016Begin Run Time: Tue Dec 27 22:37:10 CST 2016End Run Time: Tue Dec 27 22:37:13 CST 2016Process finished with exit code 0
不延時的情況下，當(dāng)早于基準(zhǔn)時間時，時間差內(nèi)的執(zhí)行任務(wù)未補償完時，下一次執(zhí)行任務(wù)的時間參考的是上一次執(zhí)行任務(wù)的結(jié)束時間；一旦補償完畢（注意粗體時間點），下一次執(zhí)行任務(wù)的時間參考的是上一次執(zhí)行任務(wù)的開始時間；當(dāng)晚于基準(zhǔn)時間時，下一次執(zhí)行任務(wù)的時間參考的是上一次執(zhí)行任務(wù)的開始時間。
scheduleAtFixedRate延時
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(); } }}執(zhí)行結(jié)果
早于當(dāng)前基準(zhǔn)時間
Date = Tue Dec 27 23:01:00 CST 2016 NowTime = Tue Dec 27 23:01:19 CST 2016Begin Run Time: Tue Dec 27 23:01:19 CST 2016End Run Time: Tue Dec 27 23:01:24 CST 2016Begin Run Time: Tue Dec 27 23:01:24 CST 2016End Run Time: Tue Dec 27 23:01:29 CST 2016Begin Run Time: Tue Dec 27 23:01:29 CST 2016End Run Time: Tue Dec 27 23:01:34 CST 2016Begin Run Time: Tue Dec 27 23:01:34 CST 2016End Run Time: Tue Dec 27 23:01:39 CST 2016
晚于當(dāng)前基準(zhǔn)時間
Date = Tue Dec 27 22:28:00 CST 2016 NowTime = Tue Dec 27 22:27:55 CST 2016Begin Run Time: Tue Dec 27 22:28:00 CST 2016End Run Time: Tue Dec 27 22:28:05 CST 2016Begin Run Time: Tue Dec 27 22:28:05 CST 2016End Run Time: Tue Dec 27 22:28:10 CST 2016Begin Run Time: Tue Dec 27 22:28:10 CST 2016End Run Time: Tue Dec 27 22:28:15 CST 2016Process finished with exit code 0
延時的情況下，即使是早于基準(zhǔn)時間，由于延時效應(yīng)，根本不可能補償完畢時間差內(nèi)的執(zhí)行任務(wù)，故而在延時的情況下，下一次任務(wù)的執(zhí)行時間都是參考上一次任務(wù)結(jié)束的時間來計算。
對比總結(jié)
| 執(zhí)行任務(wù)不延時 | 執(zhí)行任務(wù)延時 | |
|---|---|---|
| 早于當(dāng)前基準(zhǔn)時間 | schedule：下一次任務(wù)的執(zhí)行時間參考的是上一次任務(wù)的開始時間來計算。 scheduleAtFixedRate：當(dāng)早于基準(zhǔn)時間時，時間差內(nèi)的執(zhí)行任務(wù)未補償完時，下一次執(zhí)行任務(wù)的時間參考的是上一次任務(wù)的結(jié)束時間；一旦補償完畢，下一次執(zhí)行任務(wù)的時間參考上一次任務(wù)的開始時間來計算。 | 二者一樣。下一次任務(wù)的執(zhí)行時間都是參考上一次任務(wù)的結(jié)束時間來計算。 |
| 晚于當(dāng)前基準(zhǔn)時間 | 二者一樣。下一次任務(wù)的執(zhí)行時間參考的是上一次任務(wù)的開始時間來計算。 | 二者一樣。下一次任務(wù)的執(zhí)行時間都是參考上一次任務(wù)的結(jié)束時間來計算。 |
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