Why Wrapper Classes do not have pool Similar to Stringpool?

Question

Integer, Character, Double, etc. -- all these are immutable classes like String. String has Stringpool to save memory but why don't these wrappers have similar pools?

I have checked: Integer has a similar pool only up to 127, but not more than that.

Answer 1

Unless someone can find a design document from Gosling, et. al., circa 1994 or so that specifically addresses this, it's impossible to say for certain.

One likely reason is that the complexity and overhead weren't deemed worth the benefit. Strings are A) a lot bigger and B) a lot more common than Integer, Long, and such, as mostly people use primitives whenever they can, only using the wrappers where they can't avoid it.