ASCIIBits clear(String chars){
  for (int i=0, n=chars.length(); i < n; ++i) {
    char ch=chars.charAt(i);
    if (ch < 64) {
      _lowerMask&=~(1L << ch);
    }
 else {
      _upperMask&=~(1L << ch);
    }
  }
  return this;
}

ASCIIBits clear ( String chars ) { for ( int i = 0 , n = chars . length ( ) ; i < n ; ++ i ) { char ch = chars . charAt ( i ) ; if ( ch < 64 ) { _lowerMask &= ~ ( 1L << ch ) ; } else { _upperMask &= ~ ( 1L << ch ) ; } } return this ; }
clears the bit ( sets to 0 ) for each character in the argument string .
