JavaAlgorithms/Maths/GCDRecursion.java

package Maths;

/** @author https://github.com/shellhub/ */
public class GCDRecursion {
  public static void main(String[] args) {
    System.out.println(gcd(20, 15)); /* output: 5 */
    System.out.println(gcd(10, 8)); /* output: 2 */
    System.out.println(gcd(gcd(10, 5), gcd(5, 10))); /* output: 5 */
  }

  /**
   * get greatest common divisor
   *
   * @param a the first number
   * @param b the second number
   * @return gcd
   */
  public static int gcd(int a, int b) {

    if (a < 0 || b < 0) {
      throw new ArithmeticException();
    }

    if (a == 0 || b == 0) {
      return Math.abs(a - b);
    }

    if (a % b == 0) {
      return b;
    } else {
      return gcd(b, a % b);
    }
  }
}