Java - operations on native short always return int, why? and how?

Question

I'm currently working with short, but every operations between shorts gives me int. I'm aware that Java doesn't provide short literals, so cast is required when declaring/assigning a new short variable.

But why standard operations (+ - / *) give an int as a result? Is it because of Java auto-boxing mechanism?

Exemple (JDK 1.8):

private short prepareValue(short value)
{
    // here: no literal, so cast, but cast is not required for test?
    short sign = (value < 0) ? (short)-1 : (short)1;

    // here: short*short=int, so casting the result
    short absValue = (short)(value * sign);

    // here: the function returns a short, but same problem as before
    value = (short)(myFunctionOnlyOnPositive(absShort) * sign);

    // ... more things
    return value;
}

I took a look into Conversions and Contexts, but I didn't find any help on it. Even the documentation on Short isn't helping (I must be dumb or something else at this point). So can someone explain to me why does Java assume short * short = int ?