Here you can find the source of gcd(int x1, int x2)
public static final int gcd(int x1, int x2)
//package com.java2s; /*/*from w ww . jav a 2s . c o m*/ * $RCSfile: MathUtil.java,v $ * $Revision: 1.1 $ * $Date: 2005/02/11 05:02:25 $ * $State: Exp $ * * Class: MathUtil * * Description: Utility mathematical methods * * * * COPYRIGHT: * * This software module was originally developed by Rapha?l Grosbois and * Diego Santa Cruz (Swiss Federal Institute of Technology-EPFL); Joel * Askel?f (Ericsson Radio Systems AB); and Bertrand Berthelot, David * Bouchard, F?lix Henry, Gerard Mozelle and Patrice Onno (Canon Research * Centre France S.A) in the course of development of the JPEG2000 * standard as specified by ISO/IEC 15444 (JPEG 2000 Standard). This * software module is an implementation of a part of the JPEG 2000 * Standard. Swiss Federal Institute of Technology-EPFL, Ericsson Radio * Systems AB and Canon Research Centre France S.A (collectively JJ2000 * Partners) agree not to assert against ISO/IEC and users of the JPEG * 2000 Standard (Users) any of their rights under the copyright, not * including other intellectual property rights, for this software module * with respect to the usage by ISO/IEC and Users of this software module * or modifications thereof for use in hardware or software products * claiming conformance to the JPEG 2000 Standard. Those intending to use * this software module in hardware or software products are advised that * their use may infringe existing patents. The original developers of * this software module, JJ2000 Partners and ISO/IEC assume no liability * for use of this software module or modifications thereof. No license * or right to this software module is granted for non JPEG 2000 Standard * conforming products. JJ2000 Partners have full right to use this * software module for his/her own purpose, assign or donate this * software module to any third party and to inhibit third parties from * using this software module for non JPEG 2000 Standard conforming * products. This copyright notice must be included in all copies or * derivative works of this software module. * * Copyright (c) 1999/2000 JJ2000 Partners. * */ public class Main { /** * Method that calculates the Greatest Common Divisor (GCD) of two * positive integer numbers. * */ public static final int gcd(int x1, int x2) { if (x1 < 0 || x2 < 0) { throw new IllegalArgumentException("Cannot compute the GCD " + "if one integer is negative."); } int a, b, g, z; if (x1 > x2) { a = x1; b = x2; } else { a = x2; b = x1; } if (b == 0) return 0; g = b; while (g != 0) { z = a % g; a = g; g = z; } return a; } /** * Method that calculates the Greatest Common Divisor (GCD) of several * positive integer numbers. * * @param x Array containing the numbers. * */ public static final int gcd(int[] x) { if (x.length < 2) { throw new Error("Do not use this method if there are less than" + " two numbers."); } int tmp = gcd(x[x.length - 1], x[x.length - 2]); for (int i = x.length - 3; i >= 0; i--) { if (x[i] < 0) { throw new IllegalArgumentException("Cannot compute the least " + "common multiple of " + "several numbers where " + "one, at least," + "is negative."); } tmp = gcd(tmp, x[i]); } return tmp; } }