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How do I get whole and fractional parts from double in jsp/java?

Answer 1

+3 A:

As some have pointed out (and I probably should have realized given your example), what you wanted was the integer and fractional parts.

To actually want the exponent and mantissa you can convert it into the IEEE 754 representation and extract the bits like this:

long bits = Double.doubleToLongBits(3.25);

boolean isNegative = (bits & 0x8000000000000000L) != 0; 
long exponent      = (bits & 0x7ff0000000000000L) >> 52;
long mantissa      =  bits & 0x000fffffffffffffL;

Rasmus Faber 2008-12-05 11:44:38

agnul 2008-12-05 12:01:24

Rasmus it wasnt a ryt outputOutput: exponent 0 and mantissa 2814749767106560and if u choose urs agnul the mantissa is 0

Vinayak.B 2008-12-05 12:07:51

Sorry mantissa will b 7318349394477056

Vinayak.B 2008-12-05 12:10:06

Broken with 4 up votes:) Although I see what the code is trying to do with taking apart double value at its joints, the code doesn't seem to output the right values.

Gishu 2008-12-05 12:26:28

@agnul: I think "mantissa" usually refers to just the value of the bits. You might just convert this to the significand by (sometimes) prepending a 1 bit. But according to Wikipedia, the word mantissa is now deprecated in favor of "fraction".

Rasmus Faber 2008-12-05 13:32:55

Answer 2

A:

double value = 3.25;
double fractionalPart = value % 1;
double integralPart = value - fractionalPart;

Dan Vinton 2008-12-05 11:50:57

Answer 3

+2 A:

[Edit: The question originally asked how to get the mantissa and exponent.]

Where n is the number to get the real mantissa/exponent:

exponent = int(log(n))
mantissa = n / 10^exponent

Or, to get the answer you were looking for:

exponent = int(n)
mantissa = n - exponent

These are not Java exactly but should be easy to convert.

Stephen Darlington 2008-12-05 12:01:56

Answer 4

+1 A:

The mantissa and exponent of an IEEE double floating point number are the values such that

value = sign * (1 + mantissa) * pow(2, exponent)

if the mantissa is of the form 0.101010101_base 2 (ie its most sigificant bit is shifted to be after the binary point) and the exponent is adjusted for bias.

Since 1.6, java.lang.Math also provides a direct method to get the unbiased exponent (called getExponent(double))

However, the numbers you're asking for are the integral and fractional parts of the number, which can be obtained using

integral = Math.floor(x) fractional = x - Math.floor(x)

though you may you want to treat negative numbers differently (floor(-3.5) == -4.0), depending why you want the two parts.

I'd strongly suggest that you don't call these mantissa and exponent.

Pete Kirkham 2008-12-05 12:05:27

Answer 5

+5 A:

Google would help you if you used the right terms to search "get fractional and whole part out from double java"

http://www.java2s.com/Code/Java/Data-Type/Obtainingtheintegerandfractionalparts.htm

double num;
long iPart;
double fPart;

// Get user input
num = 2.3d;
iPart = (long) num;
fPart = num - iPart;
System.out.println("Integer part = " + iPart);
System.out.println("Fractional part = " + fPart);

Outputs:

Integer part = 2
Fractional part = 0.2999999999999998

Gishu 2008-12-05 12:15:39

And simple as well..

Vinayak.B 2008-12-05 12:38:28

Answer 6

A:

public class MyMain2 {
    public static void main(String[] args) {
        double myDub;
        myDub=1234.5678;
        long myLong;
        myLong=(int)myDub;
        myDub=(myDub%1)*10000;
        int myInt=(int)myDub;
        System.out.println(myLong + "\n" + myInt);
    }
}

2009-04-06 11:31:09

Answer 7

A:

Since this 1-year old question was kicked up by someone who corrected the question subject, and this question is been tagged with jsp, and nobody here was able to give a JSP targeted answer, here is my JSP-targeted contribution.

Use JSTL (just drop jstl-1.2.jar in /WEB-INF/lib) fmt taglib. There's a <fmt:formatNumber> tag which does exactly what you want and in a quite easy manner with help of maxFractionDigits and maxIntegerDigits attributes.

Here's an SSCCE, just copy'n'paste'n'run it.

<%@ taglib uri="http://java.sun.com/jsp/jstl/fmt" prefix="fmt" %>

<%
    // Just for quick prototyping. Don't do this in real! Use servlet/javabean.
    double d = 3.25;
    request.setAttribute("d", d);
%>

<!doctype html>
<html lang="en">
    <head>
        <title>SO question 343584</title>
    </head>
    <body>
        <p>Whole: <fmt:formatNumber value="${d}" maxFractionDigits="0" />
        <p>Fraction: <fmt:formatNumber value="${d}" maxIntegerDigits="0" />
    </body>
</html>

Output:

Whole: 3

Fraction: .25

That's it. No need to massage it with help of raw Java code.

BalusC 2010-02-13 13:20:14

Answer 8

A:

Since the fmt:formatNumber tag doesn't always yield the correct result, here is another JSP-only approach: It just formats the number as string and does the rest of the computation on the string, since that is easier and doesn't involve further floating point arithmetics.

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/functions" prefix="fn" %>

<%
  double[] numbers = { 0.0, 3.25, 3.75, 3.5, 2.5, -1.5, -2.5 };
  pageContext.setAttribute("numbers", numbers);
%>

<html>
  <body>
    <ul>
      <c:forEach var="n" items="${numbers}">
        <li>${n} = ${fn:substringBefore(n, ".")} + ${n - fn:substringBefore(n, ".")}</li>
      </c:forEach>
    </ul>
  </body>
</html>

Roland Illig 2010-03-10 11:43:24

When doesn't it yield the correct results then?

BalusC 2010-03-10 11:56:12

Just try all the numbers from my example. `fmt:formatNumber` rounds its argument, which is not wanted in this case.

Roland Illig 2010-03-14 12:16:17

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How do I get whole and fractional parts from double in jsp/java?

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