Java NumberFormat舍入模式，为什么将上半格式1.015更改为1.01而不是1.02

Question

Java代码

@Test
void a() {
    NumberFormat format = DecimalFormat.getInstance(Locale.CHINA);
    format.setMaximumFractionDigits(2);
    format.setMinimumFractionDigits(2);
    format.setCurrency(Currency.getInstance(Locale.CHINA));
    for (RoundingMode mode : RoundingMode.values()) {
        if(mode == RoundingMode.UNNECESSARY) continue;
        format.setRoundingMode(mode);
        System.out.println("Rounding mode: " + mode);
        System.out.println("--------------------------------------------------------");
        System.out.println("\t format 1.014 is " + format.format(1.014));
        System.out.println("\t format 1.015 is " + format.format(1.015));
        System.out.println("\t format 1.016 is " + format.format(1.016));
        System.out.println();
    }
}

结果：

环绕模式：UP

 format 1.014 is 1.02
 format 1.015 is 1.02
 format 1.016 is 1.02

环绕模式：DOWN

 format 1.014 is 1.01
 format 1.015 is 1.01
 format 1.016 is 1.01

环绕模式：天花板

 format 1.014 is 1.02
 format 1.015 is 1.02
 format 1.016 is 1.02

环绕模式：地板

 format 1.014 is 1.01
 format 1.015 is 1.01
 format 1.016 is 1.01

环绕模式：HALF_UP

 format 1.014 is 1.01
 format 1.015 is 1.01
 format 1.016 is 1.02

环绕模式：HALF_DOWN

 format 1.014 is 1.01
 format 1.015 is 1.01
 format 1.016 is 1.02

环绕模式：HALF_EVEN

 format 1.014 is 1.01
 format 1.015 is 1.01
 format 1.016 is 1.02

以退出代码0结束的过程

那么，有没有一种简单的方法可以将1.015格式化为1.02？（JDK 12，JDK 8）

Answer 1

那是因为1.015实际上是 1.0149999999999999023003738329862244427204132080078125

使用BigDecimal的解决方案适用于字符串

BigDecimal db = new BigDecimal("1.015");
db = db.setScale(2, BigDecimal.ROUND_HALF_UP);`

Answer 2

使用舍入模式：CEILING（向上舍入）

exec()

示例：public static Double roundUp(double n, int decimalPlace) { BigDecimal instance = new BigDecimal(Double.toString(n)); return instance.setScale(decimalPlace, RoundingMode.CEILING).doubleValue(); } -> roundUp(1.014, 2)