Timer类主要负责计划任务，也就是在指定的时间开始执行某一个任务。
方法schedule(TimerTask task, Date time)
public class Task {
private static Timer timer = new Timer();
static public class MyTask extends TimerTask{
@Override
public void run() {
System.out.println("Task运行了，时间为：" + new Date());
}
}
public static void main(String[] args) {
try {
MyTask myTask = new MyTask();
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String dateString = "2016-07-09 21:30:19";
Date date = sdf.parse(dateString);
System.out.println("main启动时间为：" + new Date());
timer.schedule(myTask, date);
} catch (Exception e) {
e.printStackTrace();
}
}
}
程序运行结果如下：
main启动时间为：Sat Jul 09 21:28:54 CST 2016
Task运行了，时间为：Sat Jul 09 21:30:19 CST 2016
任务虽然执行完了，但是进程还没有销毁。
创建Timer的源码如下：
public Timer() {
this("Timer-" + serialNumber());
}
public Timer(String name) {
thread.setName(name);
thread.start();
}
由构造方法可知，创建一个Timer就是启动一个新的线程，这个新启动的线程并不是守护线程，它就一直在运行。
将新创建的timer改成守护线程如下：
public class Task {
private static Timer timer = new Timer(true);
static public class MyTask extends TimerTask{
@Override
public void run() {
System.out.println("Task运行了，时间为：" + new Date());
}
}
public static void main(String[] args) {
try {
MyTask myTask = new MyTask();
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String dateString = "2016-07-09 21:42:19";
Date date = sdf.parse(dateString);
System.out.println("main启动时间为：" + new Date());
timer.schedule(myTask, date);
} catch (Exception e) {
e.printStackTrace();
}
}
}
此时控制台打印结果如下：
main启动时间为：Sat Jul 09 21:41:59 CST 2016
由于新创建的Timer线程是守护线程，main线程运行完成之后迅速结束当前进程的运行。TimerTask中的任务不会得到执行。
若执行任务的时间早于当前时间，则会立即执行任务。
public class Task {
private static Timer timer = new Timer();
static public class MyTask extends TimerTask{
@Override
public void run() {
System.out.println("Task运行了，时间为：" + new Date());
}
}
public static void main(String[] args) {
try {
MyTask myTask = new MyTask();
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String dateString = "2016-07-09 21:42:19";
Date date = sdf.parse(dateString);
System.out.println("main启动时间为：" + new Date());
timer.schedule(myTask, date);
} catch (Exception e) {
e.printStackTrace();
}
}
}
程序运行结果如下：
main启动时间为：Sat Jul 09 21:47:29 CST 2016
Task运行了，时间为：Sat Jul 09 21:47:29 CST 2016
多个TimerTask任务及延时的测试
Timer中允许有多个TimerTask任务
public class Task {
private static Timer timer = new Timer();
static public class MyTask1 extends TimerTask{
@Override
public void run() {
System.out.println("Task1运行了，时间为：" + new Date());
}
}
static public class MyTask2 extends TimerTask{
@Override
public void run() {
System.out.println("Task2运行了，时间为：" + new Date());
}
}
public static void main(String[] args) {
try {
MyTask1 myTask1 = new MyTask1();
MyTask2 myTask2 = new MyTask2();
SimpleDateFormat sdf1 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
SimpleDateFormat sdf2 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String dateString1 = "2016-07-09 22:04:19";
String dateString2 = "2016-07-09 22:05:19";
Date date1 = sdf1.parse(dateString1);
Date date2 = sdf2.parse(dateString2);
System.out.println("main启动时间为：" + new Date());
timer.schedule(myTask1, date1);
timer.schedule(myTask2, date2);
} catch (Exception e) {
e.printStackTrace();
}
}
}
程序运行结果如下：
main启动时间为：Sat Jul 09 22:04:09 CST 2016
Task1运行了，时间为：Sat Jul 09 22:04:19 CST 2016
Task2运行了，时间为：Sat Jul 09 22:05:19 CST 2016
TimerTask是以队列的方式一个一个被顺序执行的，所以执行的时间有可能和预期的时间不一致。如果前面的任务耗时较长，后面的任务执行时间有可能被推迟。
public class Task {
private static Timer timer = new Timer();
static public class MyTask1 extends TimerTask{
@Override
public void run() {
System.out.println("Task1运行了，时间为：" + new Date());
try {
Thread.sleep(20000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
static public class MyTask2 extends TimerTask{
@Override
public void run() {
System.out.println("Task2运行了，时间为：" + new Date());
}
}
public static void main(String[] args) {
try {
MyTask1 myTask1 = new MyTask1();
MyTask2 myTask2 = new MyTask2();
SimpleDateFormat sdf1 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
SimpleDateFormat sdf2 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String dateString1 = "2016-07-09 22:08:19";
String dateString2 = "2016-07-09 22:08:29";
Date date1 = sdf1.parse(dateString1);
Date date2 = sdf2.parse(dateString2);
System.out.println("main启动时间为：" + new Date());
timer.schedule(myTask1, date1);
timer.schedule(myTask2, date2);
} catch (Exception e) {
e.printStackTrace();
}
}
}
程序运行结果如下：
main启动时间为：Sat Jul 09 22:08:06 CST 2016
Task1运行了，时间为：Sat Jul 09 22:08:19 CST 2016
Task2运行了，时间为：Sat Jul 09 22:08:39 CST 2016
方法schedule(TimerTask task, Date firstTime, long period)
该方法的作用是在指定的日期之后，按指定的时间间隔周期性地无限循环地执行某一个任务
public class Main {
static public class MyTask extends TimerTask{
@Override
public void run() {
System.out.println("开始运行，时间：" + new Date());
}
public static void main(String[] args) {
try {
MyTask task = new MyTask();
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
Timer timer = new Timer();
String dateString = "2016-07-09 22:17:55";
Date date = sdf.parse(dateString);
System.out.println("main开始执行时间：" + new Date());
timer.schedule(task, date, 4000);
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
程序执行结果如下：
main开始执行时间：Sat Jul 09 22:17:30 CST 2016
开始运行，时间：Sat Jul 09 22:17:55 CST 2016
开始运行，时间：Sat Jul 09 22:17:59 CST 2016
开始运行，时间：Sat Jul 09 22:18:03 CST 2016
开始运行，时间：Sat Jul 09 22:18:07 CST 2016
......
TimerTask类的cancel()方法
TimerTask类的cancel()方法的作用是将自身从任务队列中清除
public class Task {
private static Timer timer = new Timer();
static public class MyTask1 extends TimerTask{
@Override
public void run() {
System.out.println("Task1运行了，时间为：" + new Date());
this.cancel();
}
}
static public class MyTask2 extends TimerTask{
@Override
public void run() {
System.out.println("Task2运行了，时间为：" + new Date());
}
}
public static void main(String[] args) {
try {
MyTask1 myTask1 = new MyTask1();
MyTask2 myTask2 = new MyTask2();
SimpleDateFormat sdf1 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
SimpleDateFormat sdf2 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String dateString1 = "2016-07-09 22:08:19";
String dateString2 = "2016-07-09 22:08:29";
Date date1 = sdf1.parse(dateString1);
Date date2 = sdf2.parse(dateString2);
System.out.println("main启动时间为：" + new Date());
timer.schedule(myTask1, date1, 4000);
timer.schedule(myTask2, date2, 4000);
} catch (Exception e) {
e.printStackTrace();
}
}
}
程序运行结果如下：
main启动时间为：Sat Jul 09 22:24:15 CST 2016
Task1运行了，时间为：Sat Jul 09 22:24:15 CST 2016
Task2运行了，时间为：Sat Jul 09 22:24:15 CST 2016
Task2运行了，时间为：Sat Jul 09 22:24:19 CST 2016
Task2运行了，时间为：Sat Jul 09 22:24:23 CST 2016
......
Timer类的cancel()方法
Timer类的cancel()方法的作用是将任务队列中的全部任务清除
public class Task {
private static Timer timer = new Timer();
static public class MyTask1 extends TimerTask{
@Override
public void run() {
System.out.println("Task1运行了，时间为：" + new Date());
timer.cancel();
}
}
static public class MyTask2 extends TimerTask{
@Override
public void run() {
System.out.println("Task2运行了，时间为：" + new Date());
}
}
public static void main(String[] args) {
try {
MyTask1 myTask1 = new MyTask1();
MyTask2 myTask2 = new MyTask2();
SimpleDateFormat sdf1 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
SimpleDateFormat sdf2 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String dateString1 = "2016-07-09 22:08:19";
String dateString2 = "2016-07-09 22:08:29";
Date date1 = sdf1.parse(dateString1);
Date date2 = sdf2.parse(dateString2);
System.out.println("main启动时间为：" + new Date());
timer.schedule(myTask1, date1, 4000);
timer.schedule(myTask2, date2, 4000);
} catch (Exception e) {
e.printStackTrace();
}
}
}
程序运行结果如下：
main启动时间为：Sat Jul 09 22:26:21 CST 2016
Task1运行了，时间为：Sat Jul 09 22:26:21 CST 2016
全部任务都被清除，并且进程被销毁。
Timer类的cancel()方法注意事项
public class Main {
static int i = 0;
static public class MyTask extends TimerTask{
@Override
public void run() {
System.out.println("正常执行：" + i);
}
}
public static void main(String[] args) throws ParseException {
while (true) {
i++;
Timer timer = new Timer();
MyTask task = new MyTask();
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String dateString = "2016-07-09 22:32:55";
Date date = sdf.parse(dateString);
timer.schedule(task, date);
timer.cancel();
}
}
}
程序运行结果如下：
......
正常执行：12466
正常执行：12486
正常执行：12592
正常执行：12656
正常执行：12773
正常执行：15554
正常执行：15968
......
这是因为Timer类中的cancel()没有争抢到queue锁，所以TimerTask类中的任务继续正常执行。
方法schedule(TimerTask task, long delay)的使用
方法schedule(TimerTask task, long delay)的作用是以当前时间为基准延迟delay毫秒数执行
public class Main {
static public class MyTask extends TimerTask{
@Override
public void run() {
System.out.println("执行时间：" + new Date());
}
}
public static void main(String[] args) throws ParseException {
Timer timer = new Timer();
MyTask task = new MyTask();
System.out.println("当前时间：" + new Date());
timer.schedule(task, 5000);
}
}
程序运行结果如下：
当前时间：Sat Jul 09 22:37:45 CST 2016
执行时间：Sat Jul 09 22:37:50 CST 2016
schedule(task, delay, period)的使用
schedule(task, delay, period)的作用是以当前时间为基准延迟delay毫秒数，以period毫秒数为间隔无限循环周期执行
public class Main {
static public class MyTask extends TimerTask{
@Override
public void run() {
System.out.println("执行时间：" + new Date());
}
}
public static void main(String[] args) throws ParseException {
Timer timer = new Timer();
MyTask task = new MyTask();
System.out.println("当前时间：" + new Date());
timer.schedule(task, 5000, 2000);
}
}
程序运行结果如下：
当前时间：Sat Jul 09 22:40:14 CST 2016
执行时间：Sat Jul 09 22:40:19 CST 2016
执行时间：Sat Jul 09 22:40:21 CST 2016
执行时间：Sat Jul 09 22:40:23 CST 2016
......
schedule方法任务不延时
public class Main {
private static Timer timer = new Timer();
private static int runCount = 0;
static public class MyTask extends TimerTask{
@Override
public void run() {
try {
System.out.println("begin run," + new Date());
Thread.sleep(1000);
System.out.println("end run," + new Date());
runCount++;
if (runCount == 5) {
timer.cancel();
}
} catch (Exception 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 dateString = "2016-07-10 10:26:35";
Date date = sdf.parse(dateString);
System.out.println("main开始时间：" + new Date());
timer.schedule(task, date, 3000);
} catch (Exception e) {
e.printStackTrace();
}
}
}
程序运行结果如下：
main开始时间：Sun Jul 10 10:26:27 CST 2016
begin run,Sun Jul 10 10:26:35 CST 2016
end run,Sun Jul 10 10:26:36 CST 2016
begin run,Sun Jul 10 10:26:38 CST 2016
end run,Sun Jul 10 10:26:39 CST 2016
begin run,Sun Jul 10 10:26:41 CST 2016
end run,Sun Jul 10 10:26:42 CST 2016
begin run,Sun Jul 10 10:26:44 CST 2016
end run,Sun Jul 10 10:26:45 CST 2016
begin run,Sun Jul 10 10:26:47 CST 2016
end run,Sun Jul 10 10:26:48 CST 2016
在不延时的情况下，如果执行任务的时间没有被延时，则下一次执行任务的时间是上一次任务的开始时间加上delay时间。
schedule方法任务延时
public class Main {
private static Timer timer = new Timer();
private static int runCount = 0;
static public class MyTask extends TimerTask{
@Override
public void run() {
try {
System.out.println("begin run," + new Date());
Thread.sleep(5000);//任务耗时5秒
System.out.println("end run," + new Date());
runCount++;
if (runCount == 5) {
timer.cancel();
}
} catch (Exception 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 dateString = "2016-07-10 17:00:00";
Date date = sdf.parse(dateString);
System.out.println("main开始时间：" + new Date());
timer.schedule(task, date, 3000);//周期为3秒
} catch (Exception e) {
e.printStackTrace();
}
}
}
程序运行结果如下：
main开始时间：Sun Jul 10 16:59:31 CST 2016
begin run,Sun Jul 10 17:00:00 CST 2016
end run,Sun Jul 10 17:00:05 CST 2016
begin run,Sun Jul 10 17:00:05 CST 2016
end run,Sun Jul 10 17:00:10 CST 2016
begin run,Sun Jul 10 17:00:10 CST 2016
end run,Sun Jul 10 17:00:15 CST 2016
begin run,Sun Jul 10 17:00:15 CST 2016
end run,Sun Jul 10 17:00:20 CST 2016
begin run,Sun Jul 10 17:00:20 CST 2016
end run,Sun Jul 10 17:00:25 CST 2016
任务执行周期为3秒，任务每次执行耗时5秒。从运行结果看，如果执行任务的时间被延时，那么下一次任务的执行时间以上一次任务“结束”时的时间为参考来计算。
scheduleAtFixedRate方法任务不延时
public class Main {
private static Timer timer = new Timer();
private static int runCount = 0;
static public class MyTask extends TimerTask{
@Override
public void run() {
try {
System.out.println("begin run," + new Date());
Thread.sleep(2000);//任务耗时2秒
System.out.println("end run," + new Date());
runCount++;
if (runCount == 5) {
timer.cancel();
}
} catch (Exception 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 dateString = "2016-07-10 17:18:00";
Date date = sdf.parse(dateString);
System.out.println("main开始时间：" + new Date());
timer.scheduleAtFixedRate(task, date, 3000);//周期为3秒
} catch (Exception e) {
e.printStackTrace();
}
}
}
程序运行结果如下：
main开始时间：Sun Jul 10 17:17:51 CST 2016
begin run,Sun Jul 10 17:18:00 CST 2016
end run,Sun Jul 10 17:18:02 CST 2016
begin run,Sun Jul 10 17:18:03 CST 2016
end run,Sun Jul 10 17:18:05 CST 2016
begin run,Sun Jul 10 17:18:06 CST 2016
end run,Sun Jul 10 17:18:08 CST 2016
begin run,Sun Jul 10 17:18:09 CST 2016
end run,Sun Jul 10 17:18:11 CST 2016
begin run,Sun Jul 10 17:18:12 CST 2016
end run,Sun Jul 10 17:18:14 CST 2016
schedule和scheduleAtFixedRate的区别在于，如果指定开始执行的时间在当前系统运行时间之前，scheduleAtFixedRate会把已经过去的时间也作为周期执行，而schedule不会把过去的时间算上。
scheduleAtFixedRate方法任务延时
public class Main5 {
private static Timer timer = new Timer();
private static int runCount = 0;
static public class MyTask extends TimerTask{
@Override
public void run() {
try {
System.out.println("begin run," + new Date());
Thread.sleep(5000);//任务耗时5秒
System.out.println("end run," + new Date());
runCount++;
if (runCount == 5) {
timer.cancel();
}
} catch (Exception 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 dateString = "2016-07-10 17:21:40";
Date date = sdf.parse(dateString);
System.out.println("main开始时间：" + new Date());
timer.scheduleAtFixedRate(task, date, 3000);//周期为3秒
} catch (Exception e) {
e.printStackTrace();
}
}
}
程序运行结果如下：
main开始时间：Sun Jul 10 17:21:35 CST 2016
begin run,Sun Jul 10 17:21:40 CST 2016
end run,Sun Jul 10 17:21:45 CST 2016
begin run,Sun Jul 10 17:21:45 CST 2016
end run,Sun Jul 10 17:21:50 CST 2016
begin run,Sun Jul 10 17:21:50 CST 2016
end run,Sun Jul 10 17:21:55 CST 2016
begin run,Sun Jul 10 17:21:55 CST 2016
end run,Sun Jul 10 17:22:00 CST 2016
begin run,Sun Jul 10 17:22:00 CST 2016
end run,Sun Jul 10 17:22:05 CST 2016
任务开始时间间隔为5秒。