double number precision n decimal in kotlin

Table of Contents

1. kotlin.math.round
2. String.format
3. BigDecimal

link: Kotlin

1. `kotlin.math.round`

import kotlin.math.roundToInt

fun Double.roundTo(decimals: Int): Double {
  var multiplier = 1.0
  repeat(decimals) { multiplier *= 10 }
  return (this * multiplier).roundToInt() / multiplier
}

2. `String.format`

import java.util.Locale

fun Number.roundTo(
  numFractionDigits: Int
) = "%.${numFractionDigits}f".format(this, Locale.ENGLISH).toDouble()

3. `BigDecimal`

import java.math.RoundingMode

fun Double.roundTo(decimals: Int) =
  this.toBigDecimal().setScale(decimals, RoundingMode.HALF_UP).toDouble()