Java decimal precision question

Question

I have a problem which I have to print with long decimal places. such as 1/3 = 0.33333333333333333333333333333333333333 (very very long) when using C, we can use printf("%.30f", a); but I don't know what to do using Java

Answer 1

You won't get that many decimal places of precision in IEEE754 binary floating point numbers in either C or Java. Your best bet would be to use BigDecimal and perform the arithmetic with a particular precision. For example:

import java.math.*;

public class Test {
    public static void main(String[] args) throws Exception {
        MathContext context = new MathContext(30);
        BigDecimal result = BigDecimal.ONE.divide(new BigDecimal(3), context);
        System.out.println(result.toPlainString());
    }
}