Just a simple implementation of Euclidean Algorithm.

Euclidean Algorithm

import java.io.*;
import java.math.*;

public class euclid{
    public static void main(String[] args) throws IOException{
        String[] strar=new String[2];
        try{
            BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
            System.out.print("Input two numbers here:");
            String str = br.readLine();
            br.close();
            //Any separator is allowed.
            str=str.replaceFirst("[^0-9]",",");
            str=str.replaceAll("[[^0-9]&&[^,]]","");
            strar=str.split(",",2);
            //No need to input in descending or ascending order.
            int[] parin = new int[2];
            int a=0;
            int b=0;
            parin[0]=Integer.parseInt(strar[0]);
            parin[1]=Integer.parseInt(strar[1]);
            a=Math.max(parin[0],parin[1]);
            b=Math.min(parin[0],parin[1]);
            int r=a%b;
            while(r!=0){
                a=b;
                b=r;
                r=a%b;
            }
            if(b==1){
                System.out.println("Coprime.");
            }else{
            System.out.println("The GCD is "+b+".");
            }
        }catch(IOException e){
            System.out.println("Exception :"+e);
        }
    }
}