How to validate certificate in java spring without installing in cacert

Question

From my Java application, I want to connect to the remote host and get the response from that host through rest. I have certificate of that site, so I installed that in lib\security\cacerts in my local environment.

Then I used following code to connect:

    URL obj = new URL("https://ip/security/sso/?"); 
    HttpsURLConnection con = (HttpsURLConnection) obj.openConnection();
    con.setRequestMethod("GET");
    con.setRequestProperty("User-Agent", USER_AGENT);
    int responseCode = con.getResponseCode();

It works perfectly locally and I am getting 200 response as expected.

But when I want to deploy this code on Kubernetes environment, that team is saying they can't install this certificate in cacerts (I don't understand much on Kubernetes ) and suggested me to keep certificate in some location and read that .jks certificate through Java code and then connect to https site.

I am not sure how to write that code. I tried this way but it did not work:

    final String allPassword = "changeit";
    SSLContext sslContext = null;

    try {
         sslContext = SSLContextBuilder.create()
                .loadKeyMaterial(ResourceUtils.getFile("C:\\certificate\\abc.jks"), allPassword.toCharArray(),
                        allPassword.toCharArray())
                .build();

    } catch (KeyManagementException | UnrecoverableKeyException | NoSuchAlgorithmException | KeyStoreException
            | CertificateException | IOException e1) {
        // TODO Auto-generated catch block
        e1.printStackTrace();
    }
    HttpClient client = HttpClients.custom().setSSLContext(sslContext).build();
    HttpGet getMethod = new HttpGet(obj.toString());
    HttpResponse response = client.execute(getMethod);

I am getting ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException

Do you have any idea how can I validate that certificate through code without installing it in cacert?