Java算术运算然后进行强制转换

Question

I have this piece of code.

        short x = 50,y=40;
        short z = (short)(x + y);//THIS COMPILES
        short z2 = (short) x + y;//THIS DOESN'T

How come the code snippet of z compiles, while z2 doesn't? When performing an arithmetic operation on short it will immediately promote it to a int. however I'm downcasting it back to short but it produces an error. Please explain. Am I missing anything?

Answer 1

This line:

(short) x + y

Can be understood like this:

short + int

Because the type cast only applies for x , not for the result of the sum. So, the result of the operation returns an int , thus the compiler exception.

Answer 2

The second line compiles, because the result of the addition is casted to a short so it can be assigned to z , a short .

The third line doesn't compile, because the cast to short only applies to x , before the addition takes place. The result of the addition of a short and an int is an int , which can't be assigned directly to a short ( z2 ).

The parentheses in the second line force the order of operations necessary for a short value to be assigned to a short variable.

Answer 3

In the z you are casting the final outcome of x+y as a whole to a short and assigned it to a short.

But in the z2 you are casting x to a short and adding it with y gives a int. SO int can't be assigned to a short. That is why you get the compile error