Challenge:

Given two strings, A and B. Find if there is a substring that appears in both A and B.

Specifications:

Several test cases will be given to you in a single file. The first line of the input will contain a single integer T, the number of test cases.

Then there will be T descriptions of the test cases. Each description contains two lines. The first line contains the string A and the second line contains the string B.

For each test case, display YES (in a newline), if there is a common substring.
Otherwise, display NO.

Implementation:

import java.util.Scanner;
import java.util.Set;
import java.util.HashSet;

public class TwoStrings {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        
        for (int i = Integer.parseInt(input.nextLine()); i> 0; i--) {
            String sub1 = toDiscreteString(input.nextLine());
            String sub2 = toDiscreteString(input.nextLine());
            boolean success;
            if (sub1.length() < sub2.length()) {
                success = hasCommonSubString(sub1, sub2);
            } else {
                success = hasCommonSubString(sub2, sub1);
            }
            System.out.println(success ? "YES" : "NO");
        }
    }

    private static boolean hasCommonSubString(String shorter, String longer) {
        for (int i = 0; i < shorter.length(); i++) {
            if (longer.indexOf(shorter.charAt(i)) > -1) {
                return true;
            }
        }
        return false;
    }

    private static String toDiscreteString(String input) {
        Set<Character> set = new HashSet<>();
        StringBuilder result = new StringBuilder();
        for (int i = 0; i < input.length(); i++) {
            if (set.add(input.charAt(i))) {
                result.append(input.charAt(i));
            }
        }
        return result.toString();
    }
}

This is a challenge found on HackerRank and passes all test cases. Is there a more efficient method? Is this overly-convoluted? Java 8 is available.