JWT

try {
            JsonObject header = new JsonObject();
            header.addProperty("alg", "HS256");
            header.addProperty("typ", "JWT");

            JsonObject playload = new JsonObject();
            playload.addProperty("iss", "pond");
            playload.addProperty("sub", "pond");

            String headerEncode = Base64.encodeToString(header.toString().getBytes(), Base64.URL_SAFE);
            String playloadEncode = Base64.encodeToString(playload.toString().getBytes(), Base64.URL_SAFE);
            
            String message = headerEncode + "." + playloadEncode;

            Mac sha256_HMAC = Mac.getInstance("HmacSHA256");
            SecretKeySpec secret_key = new SecretKeySpec("secret".getBytes(), "HmacSHA256");
            sha256_HMAC.init(secret_key);

            String hash = Base64.encodeToString(sha256_HMAC.doFinal(message.getBytes()), Base64.URL_SAFE);

            String token = message + "." + hash;

            System.out.println(token.replaceAll("\n", ""));
            return token.replaceAll("\n", "");
        } catch (Exception e) {
            e.printStackTrace();
        }