# Decimal to Fraction

• 12-15-2005, 10:24 PM
evenflow58
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.
• 12-16-2005, 11:14 PM
mr1yh1
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
• 11-02-2006, 08:47 PM
Daminan_sotd
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 :confused:

plz help ,Daminan_Sotd :WAVE:
• 11-03-2006, 08:16 AM
nspils
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.
• 11-05-2006, 09:17 AM
Daminan_sotd
but how do you you make java recognise diffrent patterns like .333333333 and .16666666 ???
• 11-05-2006, 01:12 PM
nspils
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