code: public synchronized boolean startMonitor() {
          if (this.executor != null) {
              if (this.monitorHandle == null) {
                  this.monitorHandle = this.executor.scheduleWithFixedDelay(this.monitor, this.monitorInterval, this.monitorInterval, TimeUnit.MILLISECONDS);
              }
              return true;
          }
          return false;
      }
docs: Starts the monitor if this Window has an executor.  Safe to call multiple
  times.
  @return True if the monitor was started (true will be returned if it
  was already previously started).