Synechron telephonic technical interview

Below question I was asked during the telephonic technical round by Synechron's technical member.
​And seems he himself was not aware of the possible scenarios in this question & was not clearing about his expected result. And also was not able to frame the questions properly.
​So below I am giving the question & the possible scenarios in that. Plus I am also giving my solution for these, which may not be optimal & will appreciate if anyone can help me to find the issues in this & provide me the optimal solution.

Question : Find the first repeating character in the given string of characters. Example String : abcdebaty
​Scenario 1 : Find the repeating character which is also coming before other characters in the string.
                     So in above string both 'b' & 'a' are repeated but here answer will be 'a' as it appears before 'b' in the above
​                     string.
​Scenario 2 : Find the first repeating character in the string.
​                     So here answer will be 'b' as it is first character which encountered again.

​Solution : 
import java.util.HashMap;
import java.util.HashSet;
public class RepeatedChars {
 public static void main(String[] args) {
//    String str = "abcdebaty";
//  String str = "abcde";
  String str = "abcdeabty";
  char ch = scenario1(str);
  if(ch == 0) {
   System.out.println("No character is repeated in given string....");
  } else {
   System.out.println("First repeated character is : " + ch);
  }
 }
​
 public static char scenario1(String str) {
        char ch = 0;
        int pos = str.length();
        HashMap<Character, Integer> hm = new HashMap<>();
        int i = 0;
        for(char c : str.toCharArray()) {
           if(hm.get(c) != null && pos > hm.get(c)) {
               ch = c;
               pos = hm.get(c);
           } else {
               hm.put(c, i++);
           }
       }
      return ch;
  }
 
 public static char scenario2(String str) {
  HashSet<Character> hs = new HashSet<>();
  char[] chars = str.toCharArray();  
  for(char ch : chars) {
      if(!hs.add(ch))
         return ch;
   }  
   return 0;
 }