Why does Math.floor return a double?

Question

Official Javadoc says that Math.floor() returns a double that is \"equal to a mathematical integer\", but then why shouldn\'t it return an in

Answer 1

Just as there is an integer and a floating point division in Java, there are integer and floating point ways to do floor:

double f = Math.floor(x);

or

int k = (int) x; 

but you always need to be careful with using floor with finite precision arithmetic: your calculation of x may yield something like 1.99999999 which will be floored to 1, not 2 by both forms. There are many algorithms out there that need to work around this limitation to avoid producing wrong results for some input values.