Why is Math.ceil not rounding upwards?

java math ceil
crmepham picture crmepham · Jun 5, 2014 · Viewed 7.1k times · Source

I have the following code:

int total = 6;
int perPage = 5;
double pages = total/perPage;
double ceilPages = Math.ceil(pages);
out.println(ceilPages);

Which outputs 1.0.

I thought it should output 2.0 because the result of total/perPage is 1.2.

Why is it not rounding upwards to 2.0?

Answer

Adam Yost picture Adam Yost · Jun 5, 2014

you are casting an the result of integer division to a double.

You need to cast each part of the division to double BEFORE the result.

double pages = (double)total/(double)perPage;

The rest should work

Related questions

Math.random() explanation

This is a pretty simple Java (though probably applicable to all programming) question: Math.random() returns a number between zero and one. If I want to return an integer between zero and hundred, I would do: (int) Math.floor(Math.…

Read More
How to evaluate a math expression given in string form?

I'm trying to write a Java routine to evaluate math expressions from String values like: "5+3" "10-40" "(1+10)*3" I want to avoid a lot of if-then-else statements. How can I do this?

Read More
Calculating powers of integers

Is there any other way in Java to calculate a power of an integer? I use Math.pow(a, b) now, but it returns a double, and that is usually a lot of work, and looks less clean when you …

Read More