comefrom: <awangdev>125. Valid Palindrome_3.java
code: public boolean isPalindrome(String s) {
          if (s == null || s.length() == 0) {
              return true;
          }
          
          StringBuffer sb = new StringBuffer();
          s = s.toLowerCase();
          for (int i = 0; i < s.length(); i++) {
              char c = s.charAt(i);
              if ((c <= 'z' && c >= 'a') || (c >= '0' && c <= '9')) {
                  sb.append(s.charAt(i));
              }
          }
          s = sb.toString();
          int start = 0;
          int end = s.length() - 1;
          while (start < end) {
              if (s.charAt(start) != s.charAt(end)) {
                  return false;
              }
              start++;
              end--;
          }
          return true;
      }
masked: public boolean var_0 ( String var_2 ) {
    if ( var_2 == null || var_2 . length ( ) == 0 ) {
      return true ;
    }
    StringBuffer var_7 = new StringBuffer ( ) ;
    var_2 = var_2 . toLowerCase ( ) ;
    for ( int var_9 = 0 ;
    var_9 < var_2 . length ( ) ;
    var_9 ++ ) {
      char var_11 = var_2 . charAt ( var_9 ) ;
      if ( ( var_11 <= 'z' && var_11 >= 'a' ) || ( var_11 >= '0' && var_11 <= '9' ) ) {
        var_7 . append ( var_2 . charAt ( var_9 ) ) ;
      }
    }
    var_2 = var_7 . toString ( ) ;
    int var_18 = 0 ;
    int var_20 = var_2 . length ( ) - 1 ;
    while ( var_18 < var_20 ) {
      if ( var_2 . charAt ( var_18 ) != var_2 . charAt ( var_20 ) ) {
        return false ;
      }
      var_18 ++ ;
      var_20 -- ;
    }
    return true ;
  }
  