mac command + d
BigDecimalと切り捨て
scala> val a: BigDecimal = 0.4444444444 a: BigDecimal = 0.4444444444 scala> a.setScale(1) java.lang.ArithmeticException: Rounding necessary at java.math.BigDecimal.commonNeedIncrement(BigDecimal.java:4148) at java.math.BigDecimal.needIncrement(BigDecimal.java:4204) at java.math.BigDecimal.divideAndRound(BigDecimal.java:4112) at java.math.BigDecimal.setScale(BigDecimal.java:2452) at java.math.BigDecimal.setScale(BigDecimal.java:2512) at scala.math.BigDecimal.setScale(BigDecimal.scala:662) ... 33 elided scala> a.setScale(4, scala.math.BigDecimal.RoundingMode.CEILING) res5: scala.math.BigDecimal = 0.4445