Question

I am learning a design pattern called listerner. Anyone can share with me an example of this pattern. I do not need anything related to GUI like JWT, Thanks

Answer 1

Listener pattern is very close to Observer. Basically you just allow other objects to “listen” to your object. Therefore you need to maintain a list of those listeners, and notify them whenever it’s needed.

Something like this:

public class MyClass {
   public static interface Listener {
      public void onNotify();
   }

   private List<Listener> listeners = new ArrayList<Listener>();

   // addListener and removeListener methods omitted.

   public void doSomething() {
      // do something that listeners should be notified of.

      // notify listeners like this:
      for (Listener l : listeners) {
         l.onNotify();
      }
   }
}

Hope it makes sense 🙂