protected static final String toAsciiLowerCase(CharSequence str) {
        if (str == null) {
            return null;
        }
        char[] buf = new char[str.length()];
        for (int i = 0; i < str.length(); i++) {
            char c = str.charAt(i);
            if (c >= 'A' && c <= 'Z') {
                c += 0x20;
            }
            buf[i] = c;
        }
        return new String(buf);
    }
Checks if a UTF-16 code unit represents a whitespace character (U+0020, 
U+0009, U+000C, U+000D or U+000A).
@param c the code unit
@return <code>true</code> if whitespace, <code>false</code> otherwise
src/nu/validator/datatype/AbstractDatatype.java