long currentTime, executionTime;
task = queue.getMin();
synchronized (task.lock) {
if (task.state == TimerTask.CANCELLED) {
queue.removeMin();
continue; // No action required, poll queue again
}
currentTime = System.currentTimeMillis();
executionTime = task.nextExecutionTime;
if (taskFired = (executionTime <= currentTime)) {
if (task.period == 0) { // Non-repeating, remove
queue.removeMin();
task.state = TimerTask.EXECUTED;
} else { // Repeating task, reschedule
queue
.rescheduleMin(task.period < 0 currentTime
- task.period
: executionTime + task.period);
}
}
}
if (!taskFired) // Task hasn't yet fired; wait
queue.wait(executionTime - currentTime);
}
if (taskFired) // Task fired; run it, holding no locks
task.run();
} catch (InterruptedException e) {
}
}
}
}
3.Timer类的主体和主要对外提供的方法
Java代码
import java.util.*;
import java.util.Date;
public class Timer {
// 定时任务队列
private TaskQueue queue = new TaskQueue();
// 计时器线程
private TimerThread thread = new TimerThread(queue);
private Object threadReaper = new Object() {
protected void finalize() throws Throwable {
synchronized (queue) {
thread.newTasksMayBeScheduled = false;
queue.notify(); // In case queue is empty.
}
}
};
// ID号作为线程的ID
private static int nextSerialNumber = 0;
private static synchronized int serialNumber() {
return nextSerialNumber++;
}
public Timer() {
this("Timer-" + serialNumber());
}
// 创建一个新计时器，可以指定其相关的线程作为守护程序运行。
public Timer(boolean isDaemon) {
this("Timer-" + serialNumber(), isDaemon);
}
public Timer(String name) {
thread.setName(name);
thread.start();
}
// 创建一个新计时器，其相关的线程具有指定的名称，并且可以指定作为守护程序运行。
public Timer(String name, boolean isDaemon) {
thread.setName(name);
thread.setDaemon(isDaemon); 织梦内容管理系统
thread.start();
}
// 安排在指定延迟后执行指定的任务。时间单位毫秒
public void schedule(TimerTask task, long delay) {
if (delay < 0)
throw new IllegalArgumentException("Negative delay.");
sched(task, System.currentTimeMillis() + delay, 0);
}
// 安排在指定的时间执行指定的任务。
public void schedule(TimerTask task, Date time) {
sched(task, time.getTime(), 0);
}
// 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。
public void schedule(TimerTask task, long delay, long period) {
if (delay < 0)
throw new IllegalArgumentException("Negative delay.");
if (period <= 0)
throw new IllegalArgumentException("Non-positive period.");
sched(task, System.currentTimeMillis() + delay, -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。
public void schedule(TimerTask task, Date firstTime, long period) {
if (period <= 0)
throw new IllegalArgumentException("Non-positive period.");
sched(task, firstTime.getTime(), -period);
}
// 安排指定的任务在指定的延迟后开始进行重复的固定速率执行。
public void scheduleAtFixedRate(TimerTask task, long delay, long period) {
if (delay < 0)
throw new IllegalArgumentException("Negative delay.");
if (period <= 0)
throw new IllegalArgumentException("Non-positive period.");
sched(task, System.currentTimeMillis() + delay, period);
}
// 安排指定的任务在指定的时间开始进行重复的固定速率执行。
public void scheduleAtFixedRate(TimerTask task, Date firstTime, long period) {
if (period <= 0)
throw new IllegalArgumentException("Non-positive period.");
sched(task, firstTime.getTime(), period);
}
private void sched(Ti