code: public void open(final ServiceTracker<?, ?> tracker) {
          if (System.getSecurityManager() == null) {
              tracker.open();
              return;
          }
          AccessController.doPrivileged(new PrivilegedAction<Void>() {
              @Override
              public Void run() {
                  tracker.open();
                  return null;
              }
          }, controlContext);
      }
docs: Opens a ServiceTracker. Same as calling tracker.open()
  
  @param tracker the ServiceTracker to open.