SCJP: can't widen and then box, but you can box and then widen

Question

I\'m studying for the SCJP exam and I ran into an issue I can\'t really wrap my head around.

The book says you can\'t widen and then box, but you can box and then wi

Answer 1

It isn't a widening because Byte doesn't fit in a Long. That's why it doesn't works.

You can box into a Byte and then widen into an Object or a Number.

As your book says :

we're back to trying to widen a Byte to a Long

---

In your case, I suppose the code looks like this :

byte b = 1;
Long l = b;

b is changed into a Byte (boxing first) but can't be changed into a Long because Byte isn't a subclass of Long.

In more steps :

byte b = 1;
Byte byteB = b; //works
Long l = byteB; //doesn't work