Java NumberFormat四舍五入模式，为什么半上格式1.015转1.01不转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:

舍入模式:UP

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

舍入模式:DOWN

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

舍入模式:CEILING

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

舍入模式:FLOOR

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

舍入模式:HALF_UP

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

舍入模式:HALF_DOWN

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

舍入模式:HALF_EVEN

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

进程结束，退出代码为 0

那么，有没有一种简单的方法可以让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);`