How to convert decimal to fractions?

Question

What I need to convert decimal to fractions. It is easy to convert to 10\'s feet.

1.5 => 15/10

This can do via this code:

Answer 1

Including the method to find highest common factor and modifying toString method, solves your question i suppose.

public String toString() {
        int hcf = findHighestCommonFactor(num, denom);
        return (String.valueOf(num/hcf) + "/" + String.valueOf(denom/hcf));

    }

    private int findHighestCommonFactor(int num, int denom) {
        if (denom == 0) {
            return num;
        }
        return findHighestCommonFactor(denom, num % denom);
    }

Answer 2

Well check this simple implementation, I have not used any GCD or something, instead, I have put the logic for the numerator and keep on incrementing till the logic is not fulfilled.

public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);
    
    System.out.println("Enter the decimal number:");
    double d = scan.nextDouble();
    
    int denom = 1;
    boolean b = true;
    while(b) {
        String[] s = String.valueOf(d * denom).split("\\.");
        if(s[0].equals(String.valueOf((int)(d * denom))) && s[1].equals("0")) {
            break;
        }
        denom++;
    }
    
    if(denom == 1) {
        System.out.println("Input a decimal number");
    }
    else {
        System.out.print("Fraction: ");
        System.out.print((int)(d*denom)+"/"+denom);
    }
}

Answer 3

Given double x >= 0, int p, int q, find p/q as closest approximation:

• iterate on q from 1 upwards, determine p above and below; check deviations

So (not tested):

public static Rational toFraction(double x) {
    // Approximate x with p/q.
    final double eps = 0.000_001;
    int pfound = (int) Math.round(x);
    int qfound = 1;
    double errorfound = Math.abs(x - pfound);
    for (int q = 2; q < 100 && error > eps; ++q) {
        int p = (int) (x * q);
        for (int i = 0; i < 2; ++i) { // below and above x
            double error = Math.abs(x - ((double) p / q));
            if (error < errorfound) {
                pfound = p;
                qfound = q;
                errorfound = error;
            }
            ++p;
        }
    }
    return new Rational(pfound, qfound);
}

You could try it for Math.PI and E.

Answer 4

I prepared a solution for this question. Maybe it's look like primitive but working. I tested many decimal number. At least it can converting 1.5 to 3/2 :)

public String kesirliYap(Double sayi){
    String[] a=payPaydaVer(sayi);
    return a[0]+"/"+a[1];
}
public String[] payPaydaVer(Double sayi){
long pay;
long payda;

  DecimalFormat df=new DecimalFormat("#");
    df.setRoundingMode(RoundingMode.FLOOR);
    String metin=sayi.toString();        
    int virguldenSonra=(metin.length() -metin.indexOf("."))-1;
    double payyda=Math.pow(10,virguldenSonra);
    double payy=payyda*sayi;
    String pays=df.format(payy);
    String paydas=df.format(payyda);
    pay=Long.valueOf(pays);
    payda=Long.valueOf(paydas);


   String[] kesir=sadelestir(pay,payda).split(",");

   return kesir;
}

private String sadelestir(Long pay,Long payda){
    DecimalFormat df=new DecimalFormat("#");
    df.setRoundingMode(RoundingMode.FLOOR);
    Long a=pay<payda ? pay : payda;
    String b = "",c = "";
    int sayac=0;
    for(double i = a;i>1;i--){
      double payy=pay/i;
      double paydaa=payda/i;
      String spay=df.format(payy);
      String spayda=df.format(paydaa);
      Long lpay=Long.valueOf(spay);
      Long lpayda=Long.valueOf(spayda);
      if((payy-lpay)==0&&(paydaa-lpayda)==0){
          b=df.format(pay/i);
          c=df.format(payda/i);
          sayac++;
          break;
      }

    }

    return sayac>0 ?  b+","+c:pay+","+payda;
}