private final boolean digit;

    private final boolean letter;

    public CharTypeFilterFactory(final IndexSettings indexSettings, final Environment environment, final String name,
            final Settings settings) {
        super(indexSettings, name, settings);

        alphabetic = settings.getAsBoolean("alphabetic", true);
        digit = settings.getAsBoolean("digit", true);

        assertTrue(CharUtil.isUrlChar('A')); // first uppercase
        assertTrue(CharUtil.isUrlChar('Z')); // last uppercase
        assertTrue(CharUtil.isUrlChar('0')); // first digit
        assertTrue(CharUtil.isUrlChar('9')); // last digit

        // Test characters just outside ranges that are not valid
        assertFalse(CharUtil.isUrlChar('`')); // backtick (just before 'a')

    /**
     * ISO 8601 extended UTC format: yyyy-MM-dd'T'HH:mm:ss.SSS'Z'
     */
    public static final String DATE_FORMAT_ISO_8601_EXTEND_UTC = "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'";

    /**
     * Digit only date format: yyyyMMddHHmmss
     */
    public static final String DATE_FORMAT_DIGIT_ONLY = "yyyyMMddHHmmss";

    /**
     * Do not instantiate.
     */
    protected CoreLibConstants() {
    }

public class Hexdump {

    /**
     * Default constructor.
     */
    public Hexdump() {
        // Utility class - no instance variables to initialize
    }

    /**
     * Array of hexadecimal digit characters used for converting binary data to hex representation.
     */
    public static final char[] HEX_DIGITS = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };

    /**

        assertFalse(UniAddress.isAllDigits(nonNumeric));
    }

    @Test
    void isAllDigitsHandlesEmptyString() {
        // Empty string technically has no non-digit characters, so it returns true
        assertTrue(UniAddress.isAllDigits(""), "isAllDigits should return true for empty string (no non-digits)");
    }

                    ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ' };

    /**
     * Array of hexadecimal digit characters used for converting binary data to hex representation.
     */
    public static final char[] HEX_DIGITS = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };

    /**