java - Using irrational numbers. Return 1/22140 . Simplify?

Question

Is this not possible? Should the fraction be simplified to avoid 'non terminating decimal expansion' public class method {

BigDecimal a = new BigDecimal("1");
BigDecimal b = new BigDecimal ("22140");
BigDecimal c;


void cal () {
    
    System.out.println(c=a.divide(b));
    
}

Answer 1

I assume you are asking if it is possible to represent 1 / 22140 exactly as a BigDecimal. The answer to that is No. The BigDecimal class cannot represent values with a non-terminating decimal expansion, and there is no simplification of the equation that will allow it.

Q: Why?

A: Basically, mathematics. 1 / 22140 cannot be represented as m * 10^s where m and s are finite integers.

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There are two practical alternative approaches:

1. You can use a MathContext argument when you do the division to specify how to round the number and how much precision to keep; e.g.

   c = a.divide(b, new MathContext(100, RoundingMode.HALF_UP));
   

   This will compute the result with 100 decimal digits of precision, rounding (in the conventional way) to the nearest representable value.

   Note that this approach gives you inexact results; e.g. (1 / 3) * 3 won't be exactly 1, no matter what you set the precision to in the MathContext.

2. You can find and use a 3rd-party Rational or Fraction class, or write your own.

   Note that Java SE doesn't provide such a class.