code: public void setInitialized() {
  
      boolean okay = (this.state == STATE_INITIALIZING);
      this.state = STATE_INITIALIZED;
      if (!okay) {
        if (isInitialized()) {
          throw new IllegalStateException("Already initialized.");
        } else {
          throw new IllegalStateException("You need to call setInitializing() before!");
        }
      }
    }
docs: This method sets the state to {@link #isInitialized() initialized}. <br>
  <b>ATTENTION:</b><br>
  You need to call {@link #setInitializing()} before you invoke this method!