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基于环形队列的超时触发算法只需要一个timer即可实现批量超时任务的触发，CPU消耗低，效率高。原理介绍，下面是此算法的简单实现。
1，TaskHolder.javapackage com.zws.timer;
/**
*
* @author wensh.zhu
* @date 2018-04-22
*/
public class TaskHolder {
/** 任务所需等待的圈数，即任务需要走几圈**/
private int cycles;
private int delays;
private Runnable task;
public TaskHolder() {}
public TaskHolder(int cycles, int delays, Runnable task) {
this.cycles = cycles;
this.delays = delays;
this.task = task;
}
public boolean isTimeOut() {
return cycles <= 0;
}
public void cutDown() {
cycles --;
}
public int getCycles() {
return cycles;
}
public void setCycles(int cycles) {
this.cycles = cycles;
}
public int getDelays() {
return delays;
}
public void setDelays(int delays) {
this.delays = delays;
}
public Runnable getTask() {
return task;
}
public void setTask(Runnable task) {
this.task = task;
}
@Override
public String toString() {
return "TaskHolder[cycles=" + cycles + ", delays=" + delays + "]";
}
}
2，TimerContext.javapackage com.zws.timer;
import java.util.Map;
import java.util.Queue;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentLinkedQueue;
/**
*
* @author wensh.zhu
* @date 2018-04-22
*/
public class TimerContext {
public static final int DEFAULT_TICKS = 60;
public static final int DEFAULT_TICK_DURATION = 1;
private Map> taskHolders;
private volatile int currentTick = 0;
/** tick一圈的长度 **/
private int ticks = DEFAULT_TICKS;
/** 每tick一次的时间间隔，单位：秒**/
private int tickDuration = DEFAULT_TICK_DURATION;
public TimerContext() {
init();
}
public TimerContext(int ticks, int tickDuration) {
if (ticks <= 0)
throw new IllegalArgumentException("ticks must be greater than 0");
if (tickDuration <= 0)
throw new IllegalArgumentException("tickDuration must be greater than 0");
this.ticks = ticks;
this.tickDuration = tickDuration;
init();
}
private void init() {
taskHolders = new ConcurrentHashMap>();
for (int i = 0; i
taskHolders.put(i, new ConcurrentLinkedQueue());
}
/**
* 添加一个定时任务并计算需要走的圈数和落脚的index
* @param task
* @param delays
*/
public void addTask(Runnable task, int delays) {
if (task == null)
throw new NullPointerException("task must not be null");
if (delays <=0)
throw new IllegalArgumentException("delays must be greater than 0");
int allSeconds = ticks * tickDuration;
int cycles = delays / allSeconds;
int index = ((delays % allSeconds) / tickDuration) + currentTick;
TaskHolder metaData = new TaskHolder(cycles, delays, task);
Queue tasks = taskHolders.get(index);
synchronized (tasks) {
tasks.add(metaData);
}
}
public int tick() {
currentTick = (currentTick + 1) % ticks;
return currentTick;
}
public Queue getCurrentTasks() {
return taskHolders.get(currentTick);
}
public int getCurrentTick() {
return currentTick;
}
public int getTicks() {
return ticks;
}
public int getTickDuration() {
return tickDuration;
}
@Override
public String toString() {
return "TimerContext [timers=" + taskHolders + ", ticks=" + ticks + ", tickDuration=" + tickDuration
+ ", currentTick=" + currentTick + "]";
}
}
3，TimerScheduler.javapackage com.zws.timer;
import java.io.IOException;
import java.util.Iterator;
import java.util.Queue;
import java.util.Timer;
import java.util.TimerTask;
/**
* 用于判断定时器是否到时、执行任务、维护定时器状态。
* @author wensh.zhu
* @date 2018-04-22
*/
public class TimerScheduler extends TimerTask {
private TimerContext timerContext;
public TimerScheduler() {}
public TimerScheduler(TimerContext timerContext) {
this.timerContext = timerContext;
}
/**
* 定时检测，如果定时器触发时间到了就从集合中删除并执行任务，否则圈数减一。
*/
@Override
public void run() {
if (timerContext == null)
return;
Queue tasks = timerContext.getCurrentTasks();
synchronized (tasks) {
Iterator itor = tasks.iterator();
while (itor.hasNext()) {
TaskHolder timer = itor.next();
if (timer.isTimeOut()) {
itor.remove();
new Thread(timer.getTask()).start();
} else {
timer.cutDown();
}
}
}
timerContext.tick();
}
public void addTask(Runnable task, int delays) {
timerContext.addTask(task, delays);
}
public TimerContext getTimerContext() {
return timerContext;
}
public void setTimerContext(TimerContext timerContext) {
this.timerContext = timerContext;
}
public static void main(String[] args) throws IOException {
TimerContext context = new TimerContext(60, 1);
TimerScheduler sheduler = new TimerScheduler(context);
sheduler.addTask(new Runnable() {
public void run() {
System.out.println(DateUtils.now());
}
}, 60);
System.out.println(DateUtils.now());
Timer timer = new Timer();
timer.scheduleAtFixedRate(sheduler, 0, context.getTickDuration() * 1000L);
System.in.read();
}
}
4，DateUtils.javapackage com.zws.timer;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
/**
*
* @author wensh.zhu
* @date 2018-04-22
*/
public class DateUtils {
public static final String DEFAULT_PATTERN = "yyyy-MM-dd HH:mm:ss";
public static String now() {
LocalDateTime time = LocalDateTime.now();
return time.format(DateTimeFormatter.ofPattern(DEFAULT_PATTERN));
}
public static String plusSeconds(int seconds) {
LocalDateTime time = LocalDateTime.now();
time.plusSeconds(seconds);
return time.format(DateTimeFormatter.ofPattern(DEFAULT_PATTERN));
}
}
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