Solved

# numeric representation/precision error

Posted on 1997-06-19
220 Views
I am relatively new to the java programming world, and having a really annoying problem with this piece of code:

import java.io.*;

class doubleTest {
public static void main(String argv[]) {
double sigDigits = 9.74;
double shiftLeft = 9.0;  // number of places to                                         shift decimal left

for (int i = 1; i <= shiftLeft; i++) {
sigDigits = sigDigits/10.0;
System.out.println(sigDigits);
}
}
}

this produces the following output:
0.974
0.0974
0.00974
9.74E-4
9.740000000000001E-5
9.740000000000002E-6
9.740000000000001E-7
9.740000000000001E-8
9.740000000000002E-9  // I get this number also if I                                  substitute for loop with:
sigDigits = Math.pow(sigDigits,-shiftLeft);

Why the extra digit at the end of the number?  Is there a better way to divide doubles that don't produce erroneous output?  If you change shiftLeft to 19.0,
you get the following output:
0.974
0.0974
0.00974
9.74E-4
9.740000000000001E-5
9.740000000000002E-6
9.740000000000001E-7
9.740000000000001E-8
9.740000000000002E-9
9.740000000000002E-10
9.740000000000002E-11
9.740000000000002E-12
9.74E-13
9.740000000000001E-14
9.740000000000001E-15
9.74E-16
9.74E-17
9.74E-18
9.74E-19

this is very strange to me.  Thanks in advance for you help.
-Matt
0
Question by:mclaren
[X]
###### Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

• Help others & share knowledge
• Earn cash & points
1 Comment

LVL 6

Accepted Solution

jpk041897 earned 50 total points
ID: 1221833
All floating point libraries introduce presition errors, the good ones simply produce them less often. Unfortunatley Java's FP lib is not amongst the best.

There are 3 possible work arrounds:

1.- If the error affect your results somhow, you will have to use native methods. See:

http://www.inf.uni-hohenheim.de/top/java/tutorial/native1.1/index.html

on how to use them.

2.- If the error only affects your results for display purposes (I.e.: the accumulated effect of the errors does not affect the values you wish to display), use formatting classes on the  output to get rid of the error. See:

http://www.acme.com/java/software/Acme.Fmt.html

for a class that will allow you to do this.
0

## Featured Post

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

### Suggested Solutions

Introduction Java can be integrated with native programs using an interface called JNI(Java Native Interface). Native programs are programs which can directly run on the processor. JNI is simply a naming and calling convention so that the JVM (Java…
In this post we will learn how to make Android Gesture Tutorial and give different functionality whenever a user Touch or Scroll android screen.
Viewers will learn about the regular for loop in Java and how to use it. Definition: Break the for loop down into 3 parts: Syntax when using for loops: Example using a for loop:
The viewer will learn how to implement Singleton Design Pattern in Java.
###### Suggested Courses
Course of the Month4 days, 22 hours left to enroll