Does the java compiler optimize repeated mathematical calculations?

The java compiler optimizes simple repetitive mathematical operations, such as:

if (prevX / width != curX / width) {
    // Do something with prevX / width value
} else {
    // Do something with curX / width value
}

I know I can assign the result to the variable and return the variable before the if statement, but it's a little troublesome If the compiler automatically recognizes that the same calculation is in progress and caches the results in temporary variables, I'd rather adhere to the above convention

*Editor - I'm an idiot I tried to ask my question simply / abstractly This is not simple: if (x > y)

Solution

The answer is yes This is called common subexpression optimization. It is a standard (powerful) compiler optimization used in Java, C / C + +

This page confirms that the hotspot JVM will perform this optimization

That is, whether the compiler / runtime can do this optimization as you expect is another matter So I usually prefer to do these optimizations myself if it also enhances readability

double xw = x / width;
double yw = y / width;

if (xw > yw) {
    return xw;
} else {
    return yw;
}