Nested Maps or combined keys in java

Question

I need a Map to make a cache in Java for same values that I have two String keys. My question it\'s better to make nested Maps (one for each key) or make some type of custom

Answer 1

Using combined keys seems more logical to me, and easier to use (you don't have to worry about the nested map being instancied).

About the combination of the keys, use a custom class. It makes more sense semantically, and prevents colisions if you have similar strings. Such a colision could appear if you have the key ["ab", "c"] and the key ["a", "bc"].

Remember when you write your custom class, you need to write the equals and hashCode methods correctly, or your cache might not work (and might suffer performance issues as well).