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1. Registered User
Join Date
Nov 2005
Posts
8

## Decimal to Fraction

I've created a Fraction class that will take a double in the constructor and transform it into a printable fraction. I've got everything working fine except for repeating fractions like 1/3. I know I need to change the code for my Fraction constructor (using doubles), but I'm not sure how.

Here is my fraction class:

public class Fraction
{
int n,d;

public Fraction()
{
n=0;
d=0;
}
public Fraction (double doubleFraction)
{
this.gcd((int)(doubleFraction*100),100);
}
public Fraction (int numerator, int denominator)
{
this.gcd(numerator,denominator);
}
private void gcd (int numerator, int denominator)
{
int highest;

if (denominator>numerator)
highest=denominator;
else
highest=numerator;

for(int x = highest;x>0;x--)
{
if (denominator%x==0 && numerator%x==0)
{
this.n=numerator/x;
this.d=denominator/x;
break;
}
}
}
public String getFraction()
{
int wholeNumber;

if (this.n == this.d)
return("" + 1);
else if (this.d > this.n)
return (this.n + "/" + this.d);
else
{
Fraction test = new Fraction(this.n,this.d);
wholeNumber = (int)(test.n/test.d);

test.gcd(test.n%test.d,test.d);

return (wholeNumber + " " + test.n + "/" + test.d);
}
}
}

Thanks for any help.
Last edited by evenflow58; 12-15-2005 at 11:57 PM.  Reply With Quote

2. Registered User
Join Date
Sep 2005
Location
istanbul / Turkey
Posts
133
1-)rational numbers may include infinite-long decimal part.
( example 1/3 ..)
and they should have a repeat pattern.
( 22/ 7 = 3.142857142857142857142857... )

2-) if we know the fraction we can find repeating part exactly.
but if we have a number with infinite-long decimal part
( should be represented using finite-precision )
we can not say exactly which is the fraction.
( each precision level may give another fraction )

problem :
in math that numbers have infinite-long decimal part.
( but inside computer they are limited ofcourse )
you work finite-long precision ( 1/100 precision ).
( but you work less precision level than java )
so , dont expect to work in java-level-precision .

forexample if you work with 1/10000 precision :
number format will be 0.xyzt
for 0.xyxy you may say xy repeating part
but this number may be 0.xyxyzxyxyz as a java double value.

guide :
-decide wich level precision you want to work .
-find the longest repeated pattern in decimal part.
- use this trick :
0.xxxxxx ===> x / 9 ( x != 9 )
0.xyxyxy ===> xy / 99 ( x != 99 )
0.xyzxyz ===> xyz / 999 ( x != 999 )
...
0.99999 =====> 1  Reply With Quote

3. Registered User
Join Date
Nov 2006
Posts
2
Hey, i need help converting decimals to fractions in java. could you post your revised program with the fixed errors? or can someone else revise it casuse i dont get how to fix it plz help ,Daminan_Sotd Last edited by Daminan_sotd; 11-02-2006 at 10:42 PM.  Reply With Quote

4. Senior Member
Join Date
Dec 2004
Location
San Bernardino County, California
Posts
1,468
Have you thought about having a lookup table for the common "infinitely repeating" decimals? Your logic could determine whether you have gone to 5(?) or 10(?) decimal places and you haven't resolved, then look up the pattern and report the fraction which follows that pattern.

For the infinitely-long non-resolving fractions, it looks like mr1yh1's suggestion will work well.  Reply With Quote

5. Registered User
Join Date
Nov 2006
Posts
2
but how do you you make java recognise diffrent patterns like .333333333 and .16666666 ???  Reply With Quote

6. Senior Member
Join Date
Dec 2004
Location
San Bernardino County, California
Posts
1,468
Read the digits after the decimal as an int and use a switch structure. Take a look at

http://java.sun.com/docs/books/jls/t...s.html#15.17.3

for performing modulus on a floating point number
Last edited by nspils; 11-05-2006 at 02:18 PM.  Reply With Quote

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