code: public void closeJARs(boolean force) {
          if (jarFiles.length > 0) {
                  synchronized (jarFiles) {
                      if (force || (System.currentTimeMillis() 
                                    > (lastJarAccessed + 90000))) {
                          for (int i = 0; i < jarFiles.length; i++) {
                              try {
                                  if (jarFiles[i] != null) {
                                      jarFiles[i].close();
                                      jarFiles[i] = null;
                                  }
                              } catch (IOException e) {
                                  if (log.isDebugEnabled()) {
                                      log.debug("Failed to close JAR", e);
                                  }
                              }
                          }
                      }
                  }
          }
      }
docs: Used to periodically signal to the classloader to release
  JAR resources.