Output seems to be correct btw
package com.codegym.task.task14.task1420;
/*
GCD
*/
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.ArrayList;
public class Solution {
public static void main(String[] args) throws Exception {
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
ArrayList<Integer> divisors1 = new ArrayList<>();
ArrayList<Integer> divisors2 = new ArrayList<>();
int number1, number2;
System.out.println("Insert 2 numbers.");
number1 = Integer.parseInt(reader.readLine());
number2 = Integer.parseInt(reader.readLine());
if (number1 <= 0) {
throw new Exception();
}
if (number2 <= 0) {
throw new Exception();
}
for (int i = 1; i <= number1 ;i++) {
if (number1 % i == 0) {
divisors1.add(i);
}
}
for (int i = 1; i <= number2 ;i++) {
if (number2 % i == 0) {
divisors2.add(i);
}
}
for (int i = divisors1.size() - 1; i >= 0; i--) {
if (divisors2.contains(divisors1.get(i))) {
System.out.println(divisors1.get(i));
break;
}
}
}
}