Java map, key = class, value = instance of that class

Question

I\'m not sure what I want to do is possible, but if it is, I want to find out how. Basically, I want to create a Map where the key is a class (java.lang.Class),

Answer 1

This isn't possible due to type erasure.

However, you could subclass HashMap and write some logic into the put method which will do this for you:

public void put(K key, V value) {

    if  ( // value is an instance of key using .getClass()) { 
        super.put(key, value)
    }
    throw new Exception();
}

(Code for illustrative purposes only)