LeetCode-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.

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

 Analysis:

Be careful that the chars should be 1-on-1 mapping.

Solution:

public class Solution {
    public boolean isIsomorphic(String s, String t) {
        if (s.length()!=t.length()) return false;
        if (s.length()==0) return true;
        
        Character[] charMap = new Character[128];
        boolean[] mapped = new boolean[128];
        char[] sArr = s.toCharArray();
        char[] tArr = t.toCharArray();
        for (int i=0;i<sArr.length;i++){
            if (charMap[sArr[i]]==null){
                if (mapped[tArr[i]]) return false;
                charMap[sArr[i]] = tArr[i];
                mapped[tArr[i]] = true;
            } else {
                if (charMap[sArr[i]]!=tArr[i]) return false;
            }
        }
        return true;
            
    }
}