JWT implementation in java

JWT.java

 public static void main(String[] args) throws NoSuchAlgorithmException, InvalidKeyException {
   
        String header = "{\"alg\":\"HS256\",\"typ\":\"JWT\"}";
        String payload = "{\"sub\":\"1234567890\",\"name\":\"John Doe\",\"iat\":1516239022}";
        
        String headerBase64 = Base64.encodeBase64URLSafeString(header.getBytes());
        String payloadBase64 = Base64.encodeBase64URLSafeString(payload.getBytes());
       
        //Create a secret to create the signature
        String secret = "your-256-bit-secret"; //this could be anything
        final SecretKeySpec secret_key = new javax.crypto.spec.SecretKeySpec(StandardCharsets.UTF_8.encode(secret).array(), "HmacSHA256");
   
        //Create the signature
        final Mac mac = Mac.getInstance("HmacSHA256");
        mac.init(secret_key);
        mac.update(headerBase64.getBytes());
        mac.update((byte)'.');
        byte[] bytes = mac.doFinal(payloadBase64.getBytes());
   
        //print
        System.out.println(headerBase64);
        System.out.println(payloadBase64);
        System.out.println(Base64.encodeBase64URLSafeString(bytes));

    }