title: How to convert all internal usage of int to BigInteger in a class
body: <p>How do I change the constructors/code so they match with the &quot;BigInteger&quot; function? I don't know how to change them and but at the same time not change the interface, nor the signature of any public constructor or public method.</p>
  <pre><code>public class RatNum {
      private int numerator;
      private int denominator;
    
  // Constructors
  public RatNum(){
      this.numerator = 0;
      this.denominator = 1;
  }
  public RatNum(int a){
      this.numerator = a;
      this.denominator = 1;
  }
  private RatNum gcd(BigInteger a, BigInteger b){
  
  }
  </code></pre>