仅 Java 8 的数字格式舍入问题
有人可以向我解释为什么下面的代码:
public class Test {
public static void main(String... args) {
round(6.2088, 3);
round(6.2089, 3);
}
private static void round(Double num, int numDecimal) {
System.out.println("BigDecimal: " + new BigDecimal(num).toString());
// Use Locale.ENGLISH for '.' as decimal separator
NumberFormat nf = NumberFormat.getInstance(Locale.ENGLISH);
nf.setGroupingUsed(false);
nf.setMaximumFractionDigits(numDecimal);
nf.setRoundingMode(RoundingMode.HALF_UP);
if(Math.abs(num) - Math.abs(num.intValue()) != 0){
nf.setMinimumFractionDigits(numDecimal);
}
System.out.println("Formatted: " + nf.format(num));
}
}
给出以下输出?
[me@localhost trunk]$ java Test
BigDecimal: 6.208800000000000096633812063373625278472900390625
Formatted: 6.209
BigDecimal: 6.208899999999999863575794734060764312744140625
Formatted: 6.208
如果您没有看到它:“6.2089”舍入为3位数字表示输出“6.208”,而“6.2088”表示“6.209”作为输出。少即是多?
使用Java 5,6或7时,结果很好,但是这个Java 8给了我这个奇怪的输出。Java 版本:
[me@localhost trunk]$ java -version
java version "1.8.0_05"
Java(TM) SE Runtime Environment (build 1.8.0_05-b13)
Java HotSpot(TM) Server VM (build 25.5-b02, mixed mode)
编辑:这是Java 7的输出:
[me@localhost trunk]$ java Test
BigDecimal: 6.208800000000000096633812063373625278472900390625
Formatted: 6.209
BigDecimal: 6.208899999999999863575794734060764312744140625
Formatted: 6.209
Java 7 版本:
[me@localhost trunk]$ java -version
java version "1.7.0_51"
Java(TM) SE Runtime Environment (build 1.7.0_51-b13)
Java HotSpot(TM) Server VM (build 24.51-b03, mixed mode)