Hands-On Design Patterns with Kotlin

Dude, where's my map?

The next day, your product manager reaches out to you. Apparently, they want a SadMap now, which gets sad each time a key is removed from it. Following the previous pattern, you extend the map again:

class SadMap<K, V>: HashMap<K, V>() {    override fun remove(key: K): V? {        println("Okay...")        return super.remove(key)    }}

But then the chief architect asks that in some cases, a map would be happy and sad at the same time. The CTO already has a great idea for a SuperSadMap that will print the following output twice:

Okay...

So, what we need is the ability to combine the behaviors of our objects.