code: public String getRequestProperty(String key) {
          if (connected)
              throw new IllegalStateException("Already connected");
  
          if (requests == null)
              return null;
  
          return requests.findValue(key);
      }
docs: Returns the value of the named general request property for this
  connection.
  
  @param key the keyword by which the request is known (e.g., "Accept").
  @return  the value of the named general request property for this
  connection. If key is null, then null is returned.
  @throws IllegalStateException if already connected
  @see #setRequestProperty(java.lang.String, java.lang.String)