How to create an alert in JavaFX?

An alert is a dialog which shows pre-built dialog types. You can create an alert by instantiating the javafx.scene.control.Alert class. This class is a subclass of the Dialog class. You can create required type of dialog bypassing the respective parameter at the time of instantiation as −

Alert alert = new Alert(Alert.AlertType.CONFIRMATION);

Example

The following Example demonstrates the creation of an Alert.

import javafx.application.Application;
import javafx.geometry.Insets;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.control.Alert;
import javafx.scene.control.Alert.AlertType;
import javafx.scene.control.Button;
import javafx.scene.control.ButtonBar.ButtonData;
import javafx.scene.control.ButtonType;
import javafx.scene.control.Dialog;
import javafx.scene.layout.HBox;
import javafx.stage.Stage;
import javafx.scene.paint.Color;
import javafx.scene.text.Font;
import javafx.scene.text.FontPosture;
import javafx.scene.text.FontWeight;
import javafx.scene.text.Text;
public class AlertExample extends Application {
   public void start(Stage stage) {
      //Creating a dialog
      Alert alert = new Alert(Alert.AlertType.CONFIRMATION);
      //Setting the title
      alert.setTitle("Alert");
      ButtonType type = new ButtonType("Ok", ButtonData.OK_DONE);
      //Setting the content of the dialog
      alert.setContentText("This is a confirmmation alert");
      //Adding buttons to the dialog pane
      alert.getDialogPane().getButtonTypes().add(type);
      //Setting the label
      Text txt = new Text("Click the button to show the dialog");
      Font font = Font.font("verdana", FontWeight.BOLD, FontPosture.REGULAR, 12);
      txt.setFont(font);
      //Creating a button
      Button button = new Button("Show Dialog");
      //Showing the dialog on clicking the button
      button.setOnAction(e -> {
         alert.showAndWait();
      });
      //Creating a vbox to hold the button and the label
      HBox pane = new HBox(15);
      //Setting the space between the nodes of a HBox pane
      pane.setPadding(new Insets(50, 150, 50, 60));
      pane.getChildren().addAll(txt, button);
      //Creating a scene object
      Scene scene = new Scene(new Group(pane), 595, 300, Color.BEIGE);
      stage.setTitle("Alert");
      stage.setScene(scene);
      stage.show();
   }
   public static void main(String args[]){
      launch(args);
   }
}

Output