Java Generics - Mixed Object Maps

Question

I'm still getting used to Java Generics however I'm currently in the process of updating an application written prior to generics to use the latest version of java.

Problem is the code was not written with type safety in mind!

We have a whole bunch of Maps that basically hold various object types including strings. For example:

Map map = new HashMap();
map.put("key1", "String1");
map.put("key2", new Date());
map.put("key3", new CutsomClass());

Now I'm still struggling with the best way to handle these without getting into refactoring a whole lot of code. Refactoring is not an option at this time.

Currently I can't see anything past Map<String, Object> although Map<String, ? super Object> works but I think its essentially the same thing ?

Answer 1

I'm still struggling with the best way to handle these without getting into refactoring a whole lot of code

So don't change them at all. The raw types - that is, the non-generic types - are still technically valid. It's not ideal and it will generate a compiler warning but the code will work (well, work as well as it ever did).

All classes extend Object so you can put any value you want into the following map:

Map<String, Object> map = new HashMap<>();

You get an additional guarantee that the key is a string, so its somewhat better than using the raw type.

Basically though, you should really try to avoid using a map if you can't define the type of the key or the value.