public Map<String, Collection<String>> headers() {
    Map<String, Collection<String>> headerMap = new TreeMap<>(String.CASE_INSENSITIVE_ORDER);
    this.headers.forEach(
        (key, headerTemplate) -> {
          List<String> values = new ArrayList<>(headerTemplate.getValues());

          /* add the expanded collection, but only if it has values */
          if (!values.isEmpty()) {
            headerMap.put(key, values);
          }
        });
    return headerMap;
  }
Returns an copy of the Headers for this request.

@return the currently applied headers.
core/src/main/java/feign/RequestTemplate.java