Isomorphic Strings

Given two strings s and t, determine if they are isomorphic.

Two strings are isomorphic if the characters in s can be replaced to get t.

All occurrences of a character must be replaced with another character while preserving the order of characters. No two characters may map to the same character but a character may map to itself.

Example 1:

Input: s = "egg", t = "add"
Output: true

Example 2:

Input: s = "foo", t = "bar"
Output: false

Example 3:

Input: s = "paper", t = "title"
Output: true

Note: You may assume both s and t have the same length.

public class Solution {
    // You may assume both s and t have the same length.
    public boolean isIsomorphic(String s, String t) {
        Map<Character, Integer> mapS = new HashMap<Character, Integer>();
        Map<Character, Integer> mapT = new HashMap<Character, Integer>();

        for (int i = 0; i < s.length(); i++) {
            int indexS = mapS.getOrDefault(s.charAt(i), -1);
            int indexT = mapT.getOrDefault(t.charAt(i), -1);

            if (indexS != indexT)
                return false;

            mapS.put(s.charAt(i), i);
            mapT.put(t.charAt(i), i);
        }

        return true;
    }
}