有没有大神帮忙解释一下这段

/** * 界面逻辑控制器， */@SuppressWarnings(“unused”)
public class FXMLDocumentController implements Initializable {
private Stage stage;
private File fileOpened;

@FXML
private TextArea textArea;

@Override
public void initialize(URL url, ResourceBundle rb) { }

void setStage(Stage stage) {
this.stage = stage;
openFile(null);
}

 private void openFile(File file) {     
    fileOpened = file;       
     if (fileOpened == null) {           
      stage.setTitle("记事本");      
        } else {                         stage.setTitle(fileOpened.getAbsolutePath());      
          }   
           }     private void readFile(File file) {      
             if (file == null) {           
              textArea.setText("");            
              return;       
               }       
                try {            
                textArea.setText(new String(Files.readAllBytes(Paths.get(file.getAbsolutePath()))));        } catch (IOException e) {            
                Alert alert = new Alert(Alert.AlertType.ERROR);            alert.setContentText("file open error: " + e.getMessage());            alert.show();        
                }   
                 }    

private void saveFileAs(File file) { try { Files.write(Paths.get(file.getAbsolutePath()), textArea.getText().getBytes());
} catch (IOException e) {
Alert alert = new Alert(Alert.AlertType.ERROR); alert.setContentText(“file write error: " + e.getMessage());
alert.show();
}
openFile(file); }
/** * 功能未实现时调用
* @param event
* */ @FXML
* private void onNotImplementedItemClick(ActionEvent event) { Alert alert = new Alert(Alert.AlertType.ERROR); String text = ((MenuItem) event.getTarget()).getText(); alert.setContentText(text + " not implemented”); alert.show();
}