練習用メモ。

AlarmListener:
#code|java|>
package timer;

public interface AlarmListener {
    public void onAlarm();
}
||<


PeriodicAlarm:
#code|java|>
package timer;

import java.util.HashSet;
import java.util.Set;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;

/**
http://www.02.246.ne.jp/~torutk/javahow2/timer.html#doc1_id120
http://d.hatena.ne.jp/AWAWA/20080423/1208955538
http://www.ibm.com/developerworks/jp/java/library/j-5things5.html
 */
public class PeriodicAlarm implements Runnable {

    ScheduledFuture future;
    ScheduledExecutorService executorService;
    final Set<AlarmListener> listeners = new HashSet<>();
    final long initialDelay;
    final long period;
    final TimeUnit timeUnit;

    public PeriodicAlarm(long initialDelay, long period, TimeUnit timeUnit) {
        this.executorService = Executors.newScheduledThreadPool(1);
        this.initialDelay = initialDelay;
        this.period = period;
        this.timeUnit = timeUnit;
    }

    public void start() {
        this.future = this.executorService.scheduleAtFixedRate(this, this.initialDelay, this.period, this.timeUnit);
    }

    public void stop() {
        this.future.cancel(true);
    }

    public void shutdown() {
        this.stop();
        this.executorService.shutdown();
    }

    public void addAlarmListener(AlarmListener l) {
        synchronized (listeners) {
            listeners.add(l);
        }
    }

    public void removeAlarmListener(AlarmListener l) {
        synchronized (listeners) {
            listeners.remove(l);
        }
    }

    @Override
    public void run() {
        synchronized (listeners) {
            for (AlarmListener l : this.listeners) {
                l.onAlarm();
            }
        }
    }
}
||<

PeriodicAlarmTest:
#code|java|>
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.concurrent.TimeUnit;
import static org.testng.Assert.*;
import org.testng.annotations.Test;
import timer.AlarmListener;
import timer.PeriodicAlarm;

public class PeriodicAlarmTest {

    public PeriodicAlarmTest() {
    }

    class Countup implements AlarmListener {

        String name;
        int count = 0;
        final SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-DD HH:mm:ss.SSS");

        public Countup(String name) {
            this.name = name;
        }

        @Override
        public void onAlarm() {
            Calendar c = Calendar.getInstance();
            String snow;
            synchronized (this.sdf) {
                snow = sdf.format(c.getTime());
            }
            count++;
            System.out.println("[" + this.name + "]:now=" + snow + ", count=" + count);

        }
    }

    @Test
    public void hello() throws InterruptedException {
        PeriodicAlarm a = new PeriodicAlarm(0, 1, TimeUnit.SECONDS);
        a.start();
        Countup c1 = new Countup("c1");
        a.addAlarmListener(c1);
        Thread.sleep(2 * 1000);
        Countup c2 = new Countup("c2");
        a.addAlarmListener(c2);
        Thread.sleep(2 * 1000);
        Countup c3 = new Countup("c3");
        a.addAlarmListener(c3);
        Thread.sleep(2 * 1000);
        a.shutdown();
        assertEquals(c1.count, 6);
        assertEquals(c2.count, 4);
        assertEquals(c3.count, 2);
    }

}
||<