Round up the last digit of whole numbers

Question

I have a number on which I need to round up the last digit, either to 0 or 5.

Examples:

1. From 0, 1, 2 to 0, for example 12 -> 10
2. From 3, 4, 5, 6, 7 to 5, like 37 -> 35
3. And from 8, 9, 0 to 0, again like 59 -> 60

I tried Math.ceil() or Math.floor() but those are not working. As I've found out those are for floating point numbers and can not be used for this problem.

Answer 1

Math.ceil and Math.floor are for floating-point numbers (like Doubles). There's no built-in function for what you want to do, but this should work

public static int round(int original) {
    if original % 10 <= 2 {
        return original - (original % 10)
    } else if original % 10 <= 7 {
        return original - (original % 10) + 5
    }
    return original - (original % 10) + 10
}

If you want it to work with negative numbers, use this:

public static int round(int original) {
    if original % 10 <= 2 {
        return original - (original % 10)
    } else if original % 10 <= 7 {
        return original - (original % 10) + 5
    } else if original % 10 <= 9 {
        return original - (original % 10) + 10
    } else if original % 10 >= -2 {
        return original - (original % 10)
    } else if original % 10 >= -7 {
        return original - (original % 10) - 5
    }
    return original - (original % 10) - 10
}

Clearly, you can't just copy & paste this code, because you'll need to put it in a class and possibly change the visibility and staticness (the public static) part.

To use it, call int rounded = round(input)

Hope this helps!