code: void activateButtons(final boolean enable) {
          this.unloadButton.setDisable(!enable);
          this.playPauseButton.setDisable(!enable);
          this.backwardButton.setDisable(!enable);
          this.forwardButton.setDisable(!enable);
          this.stopButton.setDisable(!enable);
      }
docs: Change activation of all buttons.
  
  @param enable true to enable all buttons false otherwise