Java: BigInteger floor and ceil functions [closed]

问题

It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center.

Closed 7 years ago.

I'm trying to implement an RSA attack in Java and I need to compute math operations like floor and ceil to BigInteger variables. As we know math.ceil and math.floor only apply to double variables, do you know any other way I can compute floor and ceil for BigIntegers? Thank you.

回答1:

The question does not make sense: floor and ceil round a floating number to an integer. And guess what: BigInteger can only represent Integers. So no rounding required. (Esp. the RSA context emphasize the integer character).

回答2:

Since BigInteger values are integers, I assume that you want the the ceiling and floor of division operations. For that, I suggest that you use BigDecimal instead. It has a method divide that takes another BigDecimal and a MathContext. In the MathContext, you can specify the rounding mode as ceiling or floor (among others).

If all you need is rounding toward zero, you can also use BigDecimal.divideToIntegralValue.

来源：https://stackoverflow.com/questions/9987155/java-biginteger-floor-and-ceil-functions