Question $2.(40$ pts$.)$ Our friend Willy Wazoo wrote an example to demonstrate the use of the Observer design pattern.

import java.util.$*$;

class Elevator extends Observable $\{$

private int floor;

private int max$\_$floor;

private List observers $=$ new ArrayList$()$;

public Elevator$($int max$\_$floor$)\{$

this.max$\_$floor $=$ max$\_$floor;

$\}$

public void up$()\{$

if $($this$.$floor $<=$ max$\_$floor$)\{$

this.floor$++$;

$\}$

$\}$

public void down$()\{$

if $($this$.$floor $>0)\{$

this.floor$--$;

$\}$

$\}$

public void addLight$($Observer obs$)\{$

observers.add$($obs$)$;

$\}$

$\}$

class Light implements Observer $\{$

private int floor;

private boolean state;

public Light$($int floor$)\{$

this.floor $=$ floor;

$\}$

public void setOn$()\{$

this.state $=$ true;

$\}$

public void setOff$()\{$

this.state $=$ false;

$\}$

public boolean getStatus$()\{$

return state;

$\}$

public int getFloor$()\{$

return floor;

$\}$

$\}$

class ElevatorDemo $\{$

public static final int FLOORS $=25$;

public static void main$($String$[]$ args$)\{$

Elevator anElevator $=$ new Elevator$($FLOORS$)$;

Light light;

List lights $=$ new ArrayList$()$;

for$($int i $=0$; i $<=$ FLOORS; i$++)\{$

light $=$ new Light$($i$)$;

anElevator.addLight$($light$)$;

lights.add$($light$)$;

$\}$

printLights$($lights$)$; $//$ Should print $(((0)))$ as lit and all other floors as unlit

anElevator.up$()$;

printLights$($lights$)$; $//$ Should print $(((1)))$ as lit and all other floors as unlit

anElevator.up$()$;

printLights$($lights$)$; $//$ Should print $(((2)))$ as lit and all other floors as unlit

anElevator.up$()$;

printLights$($lights$)$; $//$ Should print $(((3)))$ as lit and all other floors as unlit

anElevator.up$()$;

printLights$($lights$)$; $//$ Should print $(((4)))$ as lit and all other floors as unlit

$\}$

private static void printLights$($List lights$)\{$

ListIterator listIterator $=$ lights.listIterator$($lights$.$size$())$;

Light light;

while $($listIterator$.$hasPrevious$())\{$

light $=$ listIterator.previous$()$;

if $($light$.$getStatus$())\{$

System.out.printf$("(((\%$d$)))$

$",$ light.getFloor$())$;

$\}$

else $\{$

System.out.printf$("\%$d

$",$ light.getFloor$())$;

$\}$

$\}$

$\}$

$\}$

Unfortunately, Willy forgot something. What is it$?$ Edit the code below to help Willy implement the Observer design

pattern correctly. Do not make any unnecessary changes. Your goal is to preserve Willy$$s code as much as possible but

to make sure that it functions correctly by turning on only one light on the floor where the elevator is$.$

Which model does your implementation above follow?

$($a$)$ Pull model

$($b$)$ Push model

Change the code to implement a different model $($i$.$e$.,$ Push instead of Pull or Pull instead of Push$).$ Make sure your code

is valid Java code and has the same functionality as the original implementation. Feel free to copy the version of Willy$$s

code that you fixed, paste it in the text area below, and then edit it$.$