Alarm Clock using Java Schedular

How to implement alarm clock functionality to alarm sound at 7 am on week days and 10 am on weekends using java schedular

Steps to schedule a alarm clock during the week days or week ends

Step1. Write an abstract class wich implements Runnable and has the method to implement the logic to alarm sound.

package com.vels.test;

import java.util.TimerTask;
/**
* @author velmurugan pousel
* @project test
* created on Feb 1, 2011
*/
public abstract class SchedulerTask implements Runnable {

final Object lock = new Object();

int state = VIRGIN;
static final int VIRGIN = 0;
static final int SCHEDULED = 1;
static final int CANCELLED = 2;

TimerTask timerTask;

protected SchedulerTask() {
}

public abstract void run();

public boolean cancel() {
synchronized(lock) {
if (timerTask != null) {
timerTask.cancel();
}
boolean result = (state == SCHEDULED);
state = CANCELLED;
return result;
}
}

public long scheduledExecutionTime() {
synchronized(lock) {
return timerTask == null ? 0 : timerTask.scheduledExecutionTime();
}
}

}
Stpe 2 : Write a schedular to schedule tha alarm clock to sound


package com.vels.test;

import java.util.Date;
import java.util.Timer;
import java.util.TimerTask;
/**
* @author velmurugan pousel
* @project test
* created on Feb 1, 2011
*/
public class Scheduler {

class SchedulerTimerTask extends TimerTask {
private SchedulerTask schedulerTask;
private ScheduleIterator iterator;
public SchedulerTimerTask(SchedulerTask schedulerTask,
ScheduleIterator iterator) {
this.schedulerTask = schedulerTask;
this.iterator = iterator;
}
public void run() {
schedulerTask.run();
reschedule(schedulerTask, iterator);
}
}

private final Timer timer = new Timer();

public Scheduler() {
}

public void cancel() {
timer.cancel();
}

public void schedule(SchedulerTask schedulerTask,
ScheduleIterator iterator) {

Date time = iterator.next();
if (time == null) {
schedulerTask.cancel();
} else {
synchronized(schedulerTask.lock) {
if (schedulerTask.state != SchedulerTask.VIRGIN) {
throw new IllegalStateException("Task already scheduled " + "or cancelled");
}
schedulerTask.state = SchedulerTask.SCHEDULED;
schedulerTask.timerTask =
new SchedulerTimerTask(schedulerTask, iterator);
timer.schedule(schedulerTask.timerTask, time);
}
}
}

private void reschedule(SchedulerTask schedulerTask,
ScheduleIterator iterator) {

Date time = iterator.next();
if (time == null) {
schedulerTask.cancel();
} else {
synchronized(schedulerTask.lock) {
if (schedulerTask.state != SchedulerTask.CANCELLED) {
schedulerTask.timerTask =
new SchedulerTimerTask(schedulerTask, iterator);
timer.schedule(schedulerTask.timerTask, time);
}
}
}
}

}


Step 3 : Write an Schedule iterator


package com.vels.test;

import java.util.Date;
/**
* @author velmurugan pousel
* @project test
* created on Feb 1, 2011
*/
public interface ScheduleIterator {
public Date next();

}

Step 4 : Write a Restricted Daily Iterator - it is restricted to run a job on particular days of the week;


package com.vels.test;

import java.util.Arrays;
import java.util.Calendar;
import java.util.Date;

/**
* @author velmurugan pousel
* @project EmailScheduler
* created on Feb 2, 2011
*/
public class RestrictedDailyIterator implements ScheduleIterator {

private final int hourOfDay;
private final int minute;
private final int second;
private final int[] days;
private final Calendar calendar = Calendar.getInstance();

public RestrictedDailyIterator(int hourOfDay, int minute, int second, int day) {
this(hourOfDay, minute, second, new int[]{day});
}

public RestrictedDailyIterator(int hourOfDay, int minute, int second, int[] days) {
this(hourOfDay, minute, second, days, new Date());
}

public RestrictedDailyIterator(int hourOfDay, int minute, int second, int[] days, Date date) {
this.hourOfDay = hourOfDay;
this.minute = minute;
this.second = second;
this.days = (int[]) days.clone();
Arrays.sort(this.days);

calendar.setTime(date);
calendar.set(Calendar.HOUR_OF_DAY, hourOfDay);
calendar.set(Calendar.MINUTE, minute);
calendar.set(Calendar.SECOND, second);
calendar.set(Calendar.MILLISECOND, 0);
if (!calendar.getTime().before(date)) {
calendar.add(Calendar.DATE, -1);
}
}

public Date next() {
do {
calendar.add(Calendar.DATE, 1);
} while (Arrays.binarySearch(days, calendar.get(Calendar.DAY_OF_WEEK)) < 0);
return calendar.getTime();
}
}

Step 5 : Write Composit iterator class - takes a set of ScheduleIterators and correctly orders the dates into a single schedule.


package com.vels.test;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Date;

/**
* @author velmurugan pousel
* @project EmailScheduler
* created on Feb 2, 2011
*/
public class CompositeIterator implements ScheduleIterator {

private List orderedTimes = new ArrayList();
private List orderedIterators = new ArrayList();

public CompositeIterator(ScheduleIterator[] scheduleIterators) {
for (int i = 0; i < scheduleIterators.length; i++) {
insert(scheduleIterators[i]);
}
}

private void insert(ScheduleIterator scheduleIterator) {
Date time = scheduleIterator.next();
if (time == null) {
return;
}
int index = Collections.binarySearch(orderedTimes, time);
if (index < 0) {
index = -index - 1;
}
orderedTimes.add(index, time);
orderedIterators.add(index, scheduleIterator);
}

public synchronized Date next() {
Date next = null;
while (!orderedTimes.isEmpty() && (next == null || next.equals((Date) orderedTimes.get(0)))) {
next = (Date) orderedTimes.remove(0);
insert((ScheduleIterator) orderedIterators.remove(0));
}
return next;
}
}

Step 6 : Write an alarm clock class - it will alarm sound at 7am on week days and 9 am on weekend


package com.vels.test;

import java.text.SimpleDateFormat;

import java.util.Calendar;
import java.util.Date;


/**
* @author velmurugan pousel
* @project test
* created on Feb 1, 2011
*/
public class AlarmClock {

private final Scheduler scheduler = new Scheduler();
private final SimpleDateFormat dateFormat =
new SimpleDateFormat("dd MMM yyyy HH:mm:ss.SSS");


public AlarmClock() {
}

public void start(ScheduleIterator iterator) {

scheduler.schedule(new SchedulerTask() {
public void run() {
soundAlarm();
}
private void soundAlarm() {
System.out.println("Wake up! " +
"It's " + dateFormat.format(new Date()));
// Start a new thread to sound an alarm...
}
}, iterator);

}

public static void main(String[] args) {

int[] weekdays = new int[] {
Calendar.MONDAY,
Calendar.TUESDAY,
Calendar.WEDNESDAY,
Calendar.THURSDAY,
Calendar.FRIDAY
};
int[] weekend = new int[] {
Calendar.SATURDAY,
Calendar.SUNDAY
};
ScheduleIterator i = new CompositeIterator(
new ScheduleIterator[] {
new RestrictedDailyIterator(7, 0, 0, weekdays),
new RestrictedDailyIterator(9, 0, 0, weekend)
}
);

AlarmClock alarmClock = new AlarmClock();
alarmClock.start(i);
}


}
......


Wake up! It's 02 Feb 2011 12:28:00.011
.....




Reference : http://www.ibm.com/...