How to mock RequestEntity.put() and restTemplate.exchange() in Spock groovy

Java code for api call

I want to know how to test the below two lines of code.

private void api(){
    //Code to call an API and i want to test this in groovy spock
    HttpHeaders httpHeaders = new HttpHeaders();      
    httpHeaders.setAccept(Arrays.asList(MediaType.APPLICATION_JSON); 
    httpHeaders.setContentType(MediaType.APPLICATION_JSON);
    RestTemplate restTemplate = new RestTemplate();
    String url ="url";
    String body ="body";
    //How to mock below line
    RequestEntity<String> requestEntity = RequestEntity.put(new URI(url)).contentType(MediaType.APPLICATION_JSON).body(body);
    //And this line
    ResponseEntity<String> responseEntity = restTemplate.exchange(requestEntity,String.class);
    HttpStatus StatusCode = responseEntity.getStatusCode();
}