output: #fixed code
                                  public void downloadCompleted(URL url, File saveAs) {
          if (observer == null) {
              return;
          }
          try {
              String path = Utils.removeCWD(saveAs);
              RipStatusMessage msg = new RipStatusMessage(STATUS.DOWNLOAD_COMPLETE, path);
              itemsPending.remove(url);
              itemsCompleted.put(url, saveAs);
              observer.update(this, msg);
  
              checkIfComplete();
          } catch (Exception e) {
              logger.error("Exception while updating observer: ", e);
          }
      }
input: #vulnerable code 
                                  public void downloadCompleted(URL url, File saveAs) {
          if (observer == null) {
              return;
          }
          try {
              String path = Utils.removeCWD(saveAs);
              RipStatusMessage msg = new RipStatusMessage(STATUS.DOWNLOAD_COMPLETE, path);
              synchronized(observer) {
                  itemsPending.remove(url);
                  itemsCompleted.put(url, saveAs);
                  observer.update(this, msg);
                  observer.notifyAll();
                  checkIfComplete();
              }
          } catch (Exception e) {
              logger.error("Exception while updating observer: ", e);
          }
      } 
                              #location 8 
                              #vulnerability type THREAD_SAFETY_VIOLATION