Isomorphic Strings

https://leetcode.com/problems/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.

import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;

public class Solution {
    public static boolean isIsomorphic(String s, String t) {
        Map<Character,Integer> map=new HashMap();
        if(s.length()!=t.length()){return false;}
        boolean result=true;
        int len=s.length();
        for(int i=0;i<len;i++){
            char c=s.charAt(i);
            if(!map.containsKey(c)){
            map.put(c,i);
            }
            else{
            int index=map.get(c);
            if(t.charAt(i)!=t.charAt(index)){
                result=false;
                break;
            }
            }
        }
        if(result==false){return false;}
        
        len=t.length();
        map.clear();
        for(int i=0;i<len;i++){
            char c=t.charAt(i);
            if(!map.containsKey(c)){
            map.put(c,i);
            }
            else{
            int index=map.get(c);
            if(s.charAt(i)!=s.charAt(index)){
                result=false;
                break;
            }
            }
        }
        return result;
    }
    public static void main(String[]args){
    System.out.println(isIsomorphic("ab","aa"));
    }
}