Able to call API with Java 8 but not with 6?

Question

import com.sun.jersey.api.client.Client;
import com.sun.jersey.api.client.ClientResponse;
import com.sun.jersey.api.client.WebResource;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.json.JSONObject;

import java.io.IOException;

import static com.oxdeo.serviceclient.constants.*;

public class TokenService {
    protected final Log logger = LogFactory.getLog(TokenService.class);
    private static String bodyStr = "grant_type=client_credentials&client_id=" + coreClientId + "&client_secret=" + coreClientSecret;

    private Client jerseyClient = new Client();

    public String getToken() {
        WebResource webResource = jerseyClient.resource(coreTokenURL);
        ClientResponse clientResponse = webResource.type("application/x-www-form-urlencoded").post(ClientResponse.class, bodyStr);
        logger.info("client response  token: " + clientResponse.getStatus());
        String token = null;
        if (clientResponse.getStatus() == 200) {
            token = parseToken(clientResponse);
        } else {
            logger.error("Unable to get  token. response:" + clientResponse.getStatus());
        }
        return token;
    }

    private String parseToken(ClientResponse clientResponse) {
        String accessToken="";
        String responseStr = clientResponse.getEntity(String.class);
        JSONObject jsonResponse = new JSONObject(responseStr);
        if(clientResponse.getStatus() >=200 && clientResponse.getStatus()  <=204) {
             accessToken = jsonResponse.getString("access_token");
        }
        return accessToken;
    }

}

In the above code I running the local server on Java 1.6 and calling a API to get the token but I am getting the error like:

javax.net.ssl.SSLPeerUnverifiedException peer not authenticated

The API which I am calling may running on Java 8 OR 11, but If I run this code with Java 8 I am able to get the response. What do I need to change here or any configuration to make to return response with Java 6? I tested with the Apache library also but getting the same error with all.