Login | Register   
RSS Feed
Download our iPhone app
Browse DevX
Sign up for e-mail newsletters from DevX

By submitting your information, you agree that devx.com may send you DevX offers via email, phone and text message, as well as email offers about other products and services that DevX believes may be of interest to you. DevX will process your information in accordance with the Quinstreet Privacy Policy.

Tip of the Day
Language: Java
Expertise: Intermediate
Apr 28, 2000



Building the Right Environment to Support AI, Machine Learning and Deep Learning

BigDecimal Numbers and Formatting

[float]s and [double]s are useful for graphics and possible statistics. However they are not recommended for certain calculations requiring absolute accuracy, such as when they involve money . That's because the results produced by [float]ing point and [double] precision math is sometimes inaccurate due to data representation in the computer. Think in terms of:
double f = 2.9 - 1.1;
System.out.println( f );
giving: 1.7999999999999998 instead of 1.8

Enter the [BigDecimal] number.....

import java.math.*;

class BigDecimalTest {
  public static void main(String[] args) {
    BigDecimal a = new BigDecimal("2.9");
    BigDecimal b = new BigDecimal("1.1");
    BigDecimal c = a.subtract(b);			// Note the convention.
    System.out.println(c);				// An accurate value: 1.800000000 =)
Notice that it prints all the digits? To format it...
BigDecimal trim(BigDecimal n)		// trim ( (BigDecimal) a) to cut off all
trailing zeros
      	while (true)
			n = n.setScale(n.scale()-1);
	catch (ArithmeticException e)
// Not "real" error: No more trailing zeroes -> Just exit // setScale() tries to eliminate a non-zero digit -> Out of the loop // Remember exceptions are not recommended for exiting loops, but this seems to be the best way...

	return n;

BigDecimal format(BigDecimal n, int dp)	// Sets [n] to [dp] decimal places
	return n.setScale(dp, BigDecimal.ROUND_HALF_UP);	// Sets scale and rounds
up if most significant (cut off) number >= 5
trim(new BigDecimal("2.320000")) -> 2.32
format(new BigDecimal("1.4553"), 2) -> 1.46
format(new BigDecimal("87"), 7) -> 87.0000000
Jeremy Chen
Comment and Contribute






(Maximum characters: 1200). You have 1200 characters left.



Thanks for your registration, follow us on our social networks to keep up-to-date