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.

For example,
Given "egg", "add", return true.

Given "foo", "bar", return false.

Given "paper", "title", return true.

 

public class Solution {
    public boolean isIsomorphic(String s, String t) {
    	if (s.length() != t.length()) {
    		return false;
    	}
        HashMap<Character,Character> hashMapS = new HashMap<>();
        HashMap<Character,Character> hashMapT = new HashMap<>();
        for (int i = 0; i < s.length(); i++) {
			if (hashMapS.containsKey(s.charAt(i))) {
				if (hashMapS.get(s.charAt(i)) != t.charAt(i)) {
					return false;
				}
			} else {
				if (hashMapT.containsKey(t.charAt(i))) {
					return false;
				}
				hashMapS.put(s.charAt(i), t.charAt(i));
				hashMapT.put(t.charAt(i), s.charAt(i));
			}
		}
		return true;
    }
}