comefrom: <awangdev>205. Isomorphic Strings_1.java
code: public boolean isIsomorphic(String s, String t) {
          if (s == null || t == null || s.length() != t.length()) return false;
          Map<Character, Character> map = new HashMap<>();
          
          for (int i = 0; i < s.length(); i++) {
              char charS = s.charAt(i), charT = t.charAt(i);
              if (map.containsKey(charS)) {
                  if (map.get(charS) != charT) return false; 
              } else {
                  if (map.containsValue(charT)) return false; 
                  map.put(charS, charT);
              }
          }
          
          return true;
      }
masked: public boolean var_0 ( String var_1 , String var_2 ) {
    if ( var_1 == null || var_2 == null || var_1 . length ( ) != var_2 . length ( ) ) return false ;
    Map < Character , Character > var_3 = new HashMap < > ( ) ;
    for ( int var_4 = 0 ;
    var_4 < var_1 . length ( ) ;
    var_4 ++ ) {
      char var_5 = var_1 . charAt ( var_4 ) , var_6 = var_2 . charAt ( var_4 ) ;
      if ( var_3 . containsKey ( var_5 ) ) {
        if ( var_3 . get ( var_5 ) != var_6 ) return false ;
      }
      else {
        if ( var_3 . containsValue ( var_6 ) ) return false ;
        var_3 . put ( var_5 , var_6 ) ;
      }
    }
    return true ;
  }
  