Behavioral Design Pattern training exercice

The given source code tree simulate a (GREEN->ORANGE->RED) traffic signal including call button. States are represented as an enumeration, the traffic signal behavior being implemented in the TrafficSignal class.

Refactor this previous application using the STATE pattern so that the traffic signal behavior gets distributed among individual states.

Refactor the previous application (including STATE pattern) using the OBSERVER pattern so that:

• traffic signal updates (color changed or button pressed) are notified to a separate object (instance of TrafficSignalConsoleDisplay class)
• button pressed events are simulated by a separate thread and notified to the traffic signal object

Proper interfaces have to be defined for observers. It may also be considered that each observed object could have more than a single observer.

Once done, rewrite the application using Observer/Observable interfaces as defined in Java standard library.