code: public int getRetryAfter() {
          int retryAfter = -1;
          if (this.statusCode == 400) {
              RateLimitStatus rateLimitStatus = getRateLimitStatus();
              if (rateLimitStatus != null) {
                  retryAfter = rateLimitStatus.getSecondsUntilReset();
              }
          } else if (this.statusCode == ENHANCE_YOUR_CLAIM) {
              try {
                  String retryAfterStr = response.getResponseHeader("Retry-After");
                  if (retryAfterStr != null) {
                      retryAfter = Integer.valueOf(retryAfterStr);
                  }
              } catch (NumberFormatException ignore) {
              }
          }
          return retryAfter;
      }
docs: Returns int value of "Retry-After" response header (Search API) or seconds_until_reset (REST API).
  An application that exceeds the rate limitations of the Search API will receive HTTP 420 response codes to requests. It is a best
  practice to watch for this error condition and honor the Retry-After header that instructs the application when it is safe to
  continue. The Retry-After header's value is the number of seconds your application should wait before submitting another query (for
  example: Retry-After: 67).<br>
  Check if getStatusCode() == 503 before calling this method to ensure that you are actually exceeding rate limitation with query
  apis.<br>
  
  @return instructs the application when it is safe to continue in seconds
  @see <a href="https://dev.twitter.com/docs/rate-limiting">Rate Limiting | Twitter Developers</a>
  @since Twitter4J 2.1.0