Question

I have a map like the one below

final Map<String, ? extends Object> map

Can anyone tell me why this operation is not possible..?

productMap.put("min", String.valueof(34));

What should be the turnaround…

Answer 1

You’ve told the compiler that the map values will be some specific subtype of Object. ? could be anything — you could do:

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

So String might be invalid.

You probably want the simpler Map which does allow any value.

Or you can “cheat” and do a cast which hides the generic type:

((Map)productMap).put("min", String.valueof(34));

But that trick is not best practice & to be used sparingly if at all.