java - Adding int to short

A colleague of mine asked this question to me and I am kind of
confused.

int i =
            123456;
short x =
            12;

The
statement

x +=
            i;

Compiles fine
however

x = x +
            i;

doesn't

What
is Java doing here?

itemprop="text">

class="normal">Answer

int i = 123456;
short
            x = 12;
x +=
            i;

is
actually

int i =
            123456;
short x = 12;
x = (short)(x +
            i);

Whereas
x = x + i is simply x = x + i. It does
not automatically cast as a short and hence causes the error
(x + i is of type
int).

/>

A compound assignment
expression of the form E1 op= E2 is equivalent to
E1 = (T)((E1) op (E2)), where T is the
type of E1, except that E1 is
evaluated only once.

_{- href="http://docs.oracle.com/javase/specs/jls/se7/html/jls-15.html#jls-15.26.2"
rel="noreferrer">JLS
§15.26.2}