Why don't Java's +=, -=, *=, /= compound assignment operators require casting?

Question

Until today, I thought that for example:

i += j;

Was just a shortcut for:

i = i + j;

But if we try this:<

Answer 1

you need to cast from long to int explicitly in case of i = i + l then it will compile and give correct output. like

i = i + (int)l;

or

i = (int)((long)i + l); // this is what happens in case of += , dont need (long) casting since upper casting is done implicitly.

but in case of += it just works fine because the operator implicitly does the type casting from type of right variable to type of left variable so need not cast explicitly.