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_1 ) {
    if ( var_1 == null || var_1 . length ( ) == 0 ) {
      return true ;
    }
    StringBuffer var_2 = new StringBuffer ( ) ;
    var_1 = var_1 . toLowerCase ( ) ;
    for ( int var_3 = 0 ;
    var_3 < var_1 . length ( ) ;
    var_3 ++ ) {
      char var_4 = var_1 . charAt ( var_3 ) ;
      if ( ( var_4 <= 'z' && var_4 >= 'a' ) || ( var_4 >= '0' && var_4 <= '9' ) ) {
        var_2 . append ( var_1 . charAt ( var_3 ) ) ;
      }
    }
    var_1 = var_2 . toString ( ) ;
    int var_5 = 0 ;
    int var_6 = var_1 . length ( ) - 1 ;
    while ( var_5 < var_6 ) {
      if ( var_1 . charAt ( var_5 ) != var_1 . charAt ( var_6 ) ) {
        return false ;
      }
      var_5 ++ ;
      var_6 -- ;
    }
    return true ;
  }
  