resttemplate.getforObject(url,pojo.class) getting null in java 11, but it fetch data in java 1.8

Question

String url = "http://********";

rt = restTemplate.getForObject(url, pojoObj.getClass());

It works fine in 1.8, but when I change the compiler to Java 11 it throws an error:

org.springframework.web.client.ResourceAccessException: I/O error on GET request for "http//******": localhost; nested exception is java.net.UnknownHostException: localhost