When we have wrappers classes, why primitives are supported?

Question

We have wrapper classes in java like Interger, Float.. why it is still supportng primitives which is stoppting java to be fully object oriented language?

Answer 1

Wrappers, being objects, get placed in the heap. Primitives are just "values" and go in the stack. This is more efficient, because for wrapped primitives in the heap you need (at least) both the value (which is in the stack) and the reference to the wrapper object.

Whether this performance gain matters at all depends on what you're doing. For heavy numerical work, definitely, but for 99 % of stuff out there, this is rather an annoyance. For one thing, you can't store primitives in a Collection anyway; they get autoboxed. So the only way to store lots of them is to use plain arrays, which in turn can lead to other kinds of inefficiencies (if you need to resize them, for instance).