Java class to map a UUID to a string and back

UUIDToStringMapper.java

import java.math.BigInteger;
import java.nio.ByteBuffer;
import java.util.Base64;
import java.util.UUID;

public class UUIDToStringMapper {
    public static final long LONG_MASK = 0xFFFFFFFFFFFFFFFFL;
    private static final String CHARACTERS = "ABCDEFGHJKLMNPQRSTUVWXYZ23456789";
    private static final int KEY_LENGTH = 26;

    public static String mapUUIDToString(UUID uuid) {
        var combined = new BigInteger(1, ByteBuffer.allocate(16).putLong(uuid.getMostSignificantBits())
                .putLong(uuid.getLeastSignificantBits()).array());
        var key = new StringBuilder(KEY_LENGTH);
        for (int i = 0; i < KEY_LENGTH; i++) {
            var index = combined.and(BigInteger.valueOf(0x1fL));
            key.append(CHARACTERS.charAt(index.intValue()));
            combined = combined.shiftRight(5);
        }
        key.reverse();
        return String.format("%s-%s-%s-%s", key.substring(0, 8), key.substring(8, 13), key.substring(13, 18),
                key.substring(18));
    }

    public static String mapUUIDToBase64(UUID uuid) {
        return Base64.getUrlEncoder().withoutPadding().encodeToString(ByteBuffer.allocate(16).putLong(uuid
                .getMostSignificantBits()).putLong(uuid.getLeastSignificantBits()).array());
    }

    public static UUID mapStringToUUID(String key) {
        key = key.replaceAll("-", "").toUpperCase();
        if (key.length() != KEY_LENGTH) {
            throw new IllegalArgumentException("Invalid key length");
        }
        var combined = BigInteger.ZERO;
        for (int i = 0; i < KEY_LENGTH; i++) {
            int index = CHARACTERS.indexOf(key.charAt(i));
            if (index == -1) {
                throw new IllegalArgumentException("Invalid character in the key");
            }
            combined = combined.shiftLeft(5).or(BigInteger.valueOf(index));
        }
        return new UUID(combined.shiftRight(64).and(BigInteger.valueOf(LONG_MASK)).longValue(),
                combined.and(BigInteger.valueOf(LONG_MASK)).longValue());
    }

    public static UUID mapBase64ToUUID(String base64) {
        var byteBuffer = ByteBuffer.wrap(Base64.getUrlDecoder().decode(base64));
        return new UUID(byteBuffer.getLong(), byteBuffer.getLong());
    }

    public static void main(String[] args) {
        var uuid = UUID.randomUUID();
        var mappedString = mapUUIDToString(uuid);
        var mappedBase64 = mapUUIDToBase64(uuid);

        System.out.printf("Original UUID: %s%n", uuid);
        System.out.printf(" Without dash: %s%n", uuid.toString().replaceAll("-", ""));
        System.out.printf("Mapped String: %s%n", mappedString);
        System.out.printf(" Without dash: %s%n", mappedString.replaceAll("-", ""));
        System.out.printf("Mapped base64: %s%n%n", mappedBase64);

        System.out.printf("Reverted UUID from String: %s%n", mapStringToUUID(mappedString));
        System.out.printf("Reverted UUID from Base64: %s%n", mapBase64ToUUID(mappedBase64));
    }
}