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package model;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
/**
* Represents a log of alarm system events.
* We use the Singleton Design Pattern to ensure that there is only
* one EventLog in the system and that the system has global access
* to the single instance of the EventLog.
*/
public class EventLog implements Iterable<Event> {
/** the only EventLog in the system (Singleton Design Pattern) */
private static EventLog theLog;
private Collection<Event> events;
/**
* Prevent external construction.
* (Singleton Design Pattern).
*/
private EventLog() {
events = new ArrayList<Event>();
}
/**
* Gets instance of EventLog - creates it
* if it doesn't already exist.
* (Singleton Design Pattern)
* @return instance of EventLog
*/
public static EventLog getInstance() {
if (theLog == null) {
theLog = new EventLog();
}
return theLog;
}
/**
* Adds an event to the event log.
* @param e the event to be added
*/
public void logEvent(Event e) {
events.add(e);
}
/**
* Clears the event log and logs the event.
*/
public void clear() {
events.clear();
logEvent(new Event("Event log cleared."));
}
@Override
public Iterator<Event> iterator() {
return events.iterator();
}
}
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