public class EventListener extends Thread {

private String messageToListenFor;

private String messageToReplyWith;

private Tracker eventTracker;

public EventListener(String message, String reply) {

this(message, reply, EventTracker.getInstance());

}

public EventListener(String message, String reply, Tracker tracker) {

this.messageToListenFor = message;

this.messageToReplyWith = reply;

this.eventTracker = tracker;

}

public void run() {

while (!readyToQuit())

if (shouldReply())

reply();

}

public boolean readyToQuit() {

return eventTracker.has("quit");

}

public boolean shouldReply() {

return eventTracker.has(messageToListenFor);

}

public void reply() {

EventHandler e = () -> System.out.println(messageToReplyWith);

eventTracker.handle(messageToListenFor, e);

}

}