A Base64 UUID encoder/decoder optimised for encoding and decoding UUID hashes in only 22 characters (instead of 36)

base64uuid.java

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

public class base64uuid {
  private static final Base64.Encoder BASE64_URL_ENCODER = Base64.getUrlEncoder().withoutPadding();

  public static void main(String[] args) {
    try {
      if (args.length < 2) {
        throw new Exception("Invalid arguments");
      }

      final String op = args[0];
      final String va = args[1];

      switch (op) {
        case "encode":
          final UUID uuid = UUID.fromString(va);
          final ByteBuffer encodeBuffer = ByteBuffer.wrap(new byte[16]);
          encodeBuffer.putLong(uuid.getMostSignificantBits());
          encodeBuffer.putLong(uuid.getLeastSignificantBits());

          System.out.println(BASE64_URL_ENCODER.encodeToString(encodeBuffer.array()));

          break;
        case "decode":
          final byte[] decoded = Base64.getUrlDecoder().decode(va);
          final ByteBuffer decodeBuffer = ByteBuffer.wrap(decoded);
          final long mostSigBits = decodeBuffer.getLong();
          final long leastSigBits = decodeBuffer.getLong();

          System.out.println(new UUID(mostSigBits, leastSigBits).toString());

          break;
        default:
          throw new Exception("Invalid arguments");
      }
    } catch (Exception e) {
      System.err.println(e.getMessage());
    }
  }
}