Find the GCD for given array of elements [closed]

I had faced a interview question to find the gdc(greatest common divisor) for an integer array of element in optimised way :

Sample case :
   a[] = { 10,20,19,15,13}

Result = 1

sample case : 
  a[]={9,21,12,15,27}
Result : 3

I have submitted following result during the interview. But he asked to optimise the same. Solution which I proposesd:

package threeDpalm;

import java.util.Arrays;

public class GCF {
public static void main(String ag[]){
    GCF gcf = new GCF();
    gcf.check();
}
void check(){
    int[] input = {40,52};
    int [] original =input.clone();
    boolean flag = true; 
    int min_araay = Integer.MAX_VALUE;
    int countResult=0;
    int count=0;
    int k1=0;

    while (flag){

        countResult=0;
        count=0;
        //finding the minimum no which is greater than zero
        for (int j : input){
            if(j<min_araay && j!=0){
                min_araay = j;
                    }
                }
        // Applying Elucid algo...diving the lowesst elemt with other to remove the multiple of lowest
        for (int k=0;k<input.length; k++){
                input[k]= input [k]%min_araay;
                // if all the element are Zero, then it is the GCD..counting the Zero... 
                if(input[k]==0){
                count++;
                //if count = length ..breaking the loop
                if(count == input.length){
                    flag =false;
                            }
                        }
                }


        }
    //checking the result by diving each elemt of the array. cheking for all     the no less than that 
    for ( k1= min_araay;k1>0;k1--){
        countResult=0;
        for (int j : original){
            if (j%k1==0){
            countResult++;}}
            if (countResult==original.length){
                System.out.println(k1);
                return;
            }


        }

      }
   }

Can some one please help me with better solution