Why Java not allowed Widening and auto-boxing in single expression?

Hi All,
I have a very small question in my mind, that I would like to put on this discussion board.
Why Java not allowed Widening and auto-boxing in single expression?
Like:
short s = 10;
Long l = s;I want to know if java allowed above expression then what problem may occur?
I know it is not a intelligent question, However still I ask for discussion.
Thanks advance for all viewer of this question.

JoachimSauer wrote:
jverd wrote:
I didn't like it at first, but it turns out my initial complaints were pretty much unfounded. I find it quite useful. It takes a fair amount of clutter out of code. The only real problem with it is that if you're not careful, you can end up doing a lot of unnecessary bouncing back and forth between primitives and wrappers without knowing it, which could hurt performance.In my opinion the biggest problem is getting NPEs at code lines, that look completely harmless. That used to bother me too, but then, if I'm writing
int i = getAnInteger();it's just a replacement for
int i = getAnInteger().intValue();which would also have caused NPE.
That is, if I'm using autoboxing properly, it's just shorthand for what I'd have been doing otherwise anyway. True, it's easy to not think about it, to forget to consider whether NPE is a possibility and what the proper approach is, but mostly, if I want int, I know it can't be null (or if it is, I should get NPE).
And when it comes time to debug the NPE, it's no great mystery, once you know the rules.
If you don't think of autoboxing at the right position, then you can spend hours after hours tracking down a trivial bug ... or so I've heard ;-)Even if you're not thinking about it when you write the code, when you see an "impossible" NPE during debugging, it should be an instant giveaway.

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Why Java not allowed Widening and auto-boxing in single expression?

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