src/java.base/share/classes/java/net/CookieManager.java

*** 199,212 ****
          // pre-condition check
          if (uri == null || requestHeaders == null) {
              throw new IllegalArgumentException("Argument is null");
          }
  
-         Map<String, List<String>> cookieMap = new java.util.HashMap<>();
          // if there's no default CookieStore, no way for us to get any cookie
          if (cookieJar == null)
!             return Collections.unmodifiableMap(cookieMap);
  
          boolean secureLink = "https".equalsIgnoreCase(uri.getScheme());
          List<HttpCookie> cookies = new java.util.ArrayList<>();
          String path = uri.getPath();
          if (path == null || path.isEmpty()) {
--- 199,211 ----
          // pre-condition check
          if (uri == null || requestHeaders == null) {
              throw new IllegalArgumentException("Argument is null");
          }
  
          // if there's no default CookieStore, no way for us to get any cookie
          if (cookieJar == null)
!             return Map.of();
  
          boolean secureLink = "https".equalsIgnoreCase(uri.getScheme());
          List<HttpCookie> cookies = new java.util.ArrayList<>();
          String path = uri.getPath();
          if (path == null || path.isEmpty()) {
*** 242,253 ****
          }
  
          // apply sort rule (RFC 2965 sec. 3.3.4)
          List<String> cookieHeader = sortByPath(cookies);
  
!         cookieMap.put("Cookie", cookieHeader);
!         return Collections.unmodifiableMap(cookieMap);
      }
  
      public void
          put(URI uri, Map<String, List<String>> responseHeaders)
          throws IOException
--- 241,251 ----
          }
  
          // apply sort rule (RFC 2965 sec. 3.3.4)
          List<String> cookieHeader = sortByPath(cookies);
  
!         return Map.of("Cookie", cookieHeader);
      }
  
      public void
          put(URI uri, Map<String, List<String>> responseHeaders)
          throws IOException