Round Double to 1 decimal place kotlin: from 0.044999 to 0.1

Question

I have a Double variable that is 0.0449999 and I would like to round it to 1 decimal place 0.1 .

I am using Kotlin but the Java solution is also helpful.

val number:Double = 0.0449999

I tried getting 1 decimal place with these two solutions:

1. val solution = Math.round(number * 10.0) / 10.0
2. val solution = String.format("%.1f", number)

The problem is that I get 0.0 in both cases because it rounds the number from 0.04 to 0.0. It doesn't take all decimals and round it.

I would like to obtain 0.1: 0.045 -> 0.05 -> 0.1

Answer 1

Finally I did what Andy Turner suggested, rounded to 3 decimals, then to 2 and then to 1:

Answer 1:

val number:Double = 0.0449999 val number3digits:Double = String.format("%.3f", number).toDouble() val number2digits:Double = String.format("%.2f", number3digits).toDouble() val solution:Double = String.format("%.1f", number2digits).toDouble() 

Answer 2:

val number:Double = 0.0449999 val number3digits:Double = Math.round(number * 1000.0) / 1000.0 val number2digits:Double = Math.round(number3digits * 100.0) / 100.0 val solution:Double = Math.round(number2digits * 10.0) / 10.0 

Result:

0.045 → 0.05 → 0.1

Note: I know it is not how it should work but sometimes you need to round up taking into account all decimals for some special cases so maybe someone finds this useful.