Why shortValue() method are concrete but intValue() is abstract into java.lang.Number?

Question

I have read source code of java.lang.Number and I wondered why

1. intValue()
2. longValue()
3. floatVa

Answer 1

byte and short are the lesser memory consuming versions, and since intValue is abstract, the implementation of intValue can be used for the byte and short. I think that's why they should have done it like that.