How would I make a new fraction if a fraction cannot be simplified?

So I’m writing an assignment for my OOP class that asks the user for a number of fractions, then randomly generates that number of fractions. Part of the assignment states that if one of the fractions cannot be simplified then skip it and create a new fraction that can be simplified. However the unreducible fractions still make it through. I need a way to have the program make a new fraction if the GCD of a fraction is 1.

Code:

import java.util.Random;


 // The class is called boxes because I'm supposed to print boxes around the fractions, but I'll 
    implement it later.
    class SimpleFracBoxes{

   private int numberOfFractions = 0;
   private String result = "";  
   Random myRandom = new Random( );
   int min = 1;
   int max = 100000;
  
   public SimpleFracBoxes( )
   {
   }
   
   public SimpleFracBoxes(int nOFracs)
   {
      numberOfFractions = nOFracs;
   }
 
// makes the fractions   
   public void makeTheFractions()
   {
      for (int i = 0; i < numberOfFractions; i++)
      {
         Fraction frac = getAGoodFraction();
         Fraction frac2 = frac.simplify();
         result = result + " "+ (int)(i + 1) + ": " + frac + " simplifies to "+ frac2 + "n" ;         
     }
 }     
 // creates a fraction that can be divided           
   private Fraction getAGoodFraction()
   {  
      Fraction frac;
         do {                      
            frac = new Fraction (myRandom.nextInt(max-min), myRandom.nextInt(max-min));      
            }      
          while (frac.getNumerator() >= frac.getDenominator());
          int num = frac.getNumerator();
           int denom = frac.getDenominator();
          int gcd = frac.gcd(num, denom);        
               if (gcd == 1)  {                  
                   getAGoodFraction();
                              
                } else if (gcd !=1) {                    
                  frac.simplify();
                }              
      return frac;    
 }
   public String getFractions()
   {
      return result;
   }     
}

Fraction Class code

public class Fraction{


private int numerator;
private int denominator;

public Fraction(){
    this(0,1);
}

public Fraction(int number) {
    this(number,1);
}

public Fraction(Fraction frac) {
    this(frac.getNumerator(), frac.getDenominator());
}
public Fraction(int num, int denom){
    setNumerator(num);
    setDenominator(denom);
}

public static int gcd(int m, int n) {

    int r = n % m;

    while (r != 0) {

        n = m;

        m = r;

        r = n % m;
    }

    return m;

}

public static Fraction min(Fraction f1, Fraction f2) {

    double f1_dec = f1.decimal();
    double f2_dec = f2.decimal();

    if (f1_dec <= f2_dec) {

        return f1;

    } else {

        return f2;
    }
}

public Fraction add(Fraction frac) {

    int a, b, c, d;

    Fraction sum;

    a = this.getNumerator();
    b = this.getDenominator();
    c = frac.getNumerator();
    d = frac.getDenominator();

    sum = new Fraction(a*d + b*c, b*d);

    return sum;
}

public Fraction add(int number) {

    Fraction frac = new Fraction(number, 1);

    Fraction sum = add(frac);

    return sum;
}

public Fraction divide(Fraction frac) {

    int a, b, c, d;

    Fraction quotient;

    a = this.getNumerator();
    b = this.getDenominator();
    c = frac.getNumerator();
    d = frac.getDenominator();

    quotient = new Fraction(a*d, b*c);

    return quotient;
}

public Fraction divide(int number) {

    Fraction frac = new Fraction(number, 1);

    Fraction quotient = divide(frac);

    return quotient;
}

public boolean equals(Fraction frac) {

    Fraction f1 = simplify();

    Fraction f2 = frac.simplify();

    if (f1.getNumerator() == f2.getNumerator() &&

        f1.getDenominator() == f2.getDenominator()) {

        return true;

    } else {

        return false;
    }
}

public int getDenominator() {

    return denominator;
}

public int getNumerator(){

    return numerator;
}

public Fraction multiply(Fraction frac){

    int a, b, c, d;

    Fraction product;

    a = this.getNumerator();
    b = this.getDenominator();
    c = frac.getNumerator();
    d = frac.getDenominator();

    product = new Fraction(a*c, b*d);

    return product;
}

public Fraction multiply(int number){

    Fraction frac = new Fraction(number, 1);

    Fraction product = multiply(frac);

    return product;
}

public void setDenominator(int denom){

if (denom == 0) {

    System.err.println("Fatal Error");
    System.exit(1);
}

denominator = denom;

}

public void setNumerator(int num) {
    numerator = num;
}

public Fraction simplify(){

    int num = getNumerator();
    int denom = getDenominator();
    int gcd = gcd(num, denom);

    Fraction simp = new Fraction(num/gcd, denom/gcd);

    return simp;

}

public Fraction subtract(Fraction frac) {

    int a, b, c, d;

    Fraction diff;

    a = this.getNumerator();
    b = this.getDenominator();
    c = frac.getNumerator();
    d = frac.getDenominator();

    diff = new Fraction(a*d - b*c, b*d);

    return diff;

}

public Fraction subtract(int number) {

    Fraction frac = new Fraction(number, 1);

    Fraction difference = subtract(frac);

    return difference;
}

public String toString() {

    return getNumerator() + "/" + getDenominator();
}


private double decimal() {

    return (double) getNumerator() / getDenominator();
}

}

Output:
How many fractions? 3
 1: 28181/38503 simplifies to 28181/38503 // Unsimplified
 2: 75654/99570 simplifies to 12609/16595
 3: 787/31255 simplifies to 787/31255 // Unsimplified

Answer

• Method decimal() in class Fraction is not used, so I removed it.
• Rather than recursively call method getAGoodFraction() when the GCD value is 1, use a loop.
• Rather than create a new Fraction object each time the randomly generated numerator is greater than the randomly generated denominator, use methods setNumerator() and setDenominator(). That’s what they’re for.
• There is no need to call method simplify() in method getAGoodFraction(). Just return the fraction. Because the GCD is not equal to 1, you know it can be simplified.

Compare the following code with yours.
Note that I added a main() method to class Fraction so as to be able to run the code. And I also changed method gcd() due to the comment to your question from @KevinAnderson.

import java.util.Random;

public class Fraction {
    private int numerator;
    private int denominator;

    public Fraction() {
        this(0, 1);
    }

    public Fraction(int number) {
        this(number, 1);
    }

    public Fraction(Fraction frac) {
        this(frac.getNumerator(), frac.getDenominator());
    }

    public Fraction(int num, int denom) {
        setNumerator(num);
        setDenominator(denom);
    }

    public static int gcd(int m, int n) {
        int factor = m;
        int r = n % factor;
        while (r != 0  &&  factor > 1) {
            r = n % --factor;
            if (r == 0) {
                r = m % factor;
            }
        }
        return factor;
    }

    public int getDenominator() {
        return denominator;
    }

    public int getNumerator() {
        return numerator;
    }

    public void setDenominator(int denom) {
        if (denom == 0) {
            System.err.println("Fatal Error");
            System.exit(1);
        }
        denominator = denom;
    }

    public void setNumerator(int num) {
        numerator = num;
    }

    public Fraction simplify() {
        int num = getNumerator();
        int denom = getDenominator();
        int gcd = gcd(num, denom);

        Fraction simp = new Fraction(num / gcd, denom / gcd);
        return simp;
    }

    public String toString() {
        return getNumerator() + "/" + getDenominator();
    }

    public static void main(String[] args) {
        SimpleFracBoxes sfb = new SimpleFracBoxes(10);
        sfb.makeTheFractions();
        System.out.println(sfb.getFractions());
    }
}

class SimpleFracBoxes {
    private int numberOfFractions = 0;
    private String result = "";
    Random myRandom = new Random();
    int min = 1;
    int max = 100000;

    public SimpleFracBoxes() {
    }

    public SimpleFracBoxes(int nOFracs) {
        numberOfFractions = nOFracs;
    }

//makes the fractions   
    public void makeTheFractions() {
        for (int i = 0; i < numberOfFractions; i++) {
            Fraction frac = getAGoodFraction();
            Fraction frac2 = frac.simplify();
            result += String.format("%" + String.valueOf(numberOfFractions).length() + "d. %5d/%5d simplifies to %5d/%5d%n",
                                    (i + 1),
                                    frac.getNumerator(),
                                    frac.getDenominator(),
                                    frac2.getNumerator(),
                                    frac2.getDenominator());
        }
    }

// creates a fraction that can be divided           
    private Fraction getAGoodFraction() {
        int gcd = 1;
        Fraction frac = new Fraction();
        while (gcd == 1) {
            do {
                frac.setNumerator(myRandom.nextInt(max - min));
                frac.setDenominator(myRandom.nextInt(max - min));
            } while (frac.getNumerator() >= frac.getDenominator());
            int num = frac.getNumerator();
            int denom = frac.getDenominator();
            gcd = Fraction.gcd(num, denom);
        }
        return frac;
    }

    public String getFractions() {
        return result;
    }
}

Here is a sample output produced when running the above code.

 1. 64480/84728 simplifies to  8060/10591
 2. 33376/79317 simplifies to  4768/11331
 3. 50944/97026 simplifies to 25472/48513
 4. 21339/45510 simplifies to  7113/15170
 5. 35884/38628 simplifies to  8971/ 9657
 6. 15148/17199 simplifies to  2164/ 2457
 7. 72670/95005 simplifies to 14534/19001
 8. 19810/44730 simplifies to   283/  639
 9. 61790/63956 simplifies to 30895/31978
10.  4824/ 5352 simplifies to   201/  223