ComboBoxSample.java

import javafx.application.Application;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Insets;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.control.*;
import javafx.scene.layout.GridPane;
import javafx.scene.paint.Color;
import javafx.stage.Stage;
import javafx.util.Callback;
 
public class ComboBoxSample extends Application {
        public static void main(String[] args) {
        launch(args);
    }
    
    final Button button = new Button ("Send");
    final Label notification = new Label ();
    final TextField subject = new TextField("");
    final TextArea text = new TextArea ("");
    
    String address = " ";
    
    @Override public void start(Stage stage) {
        stage.setTitle("ComboBoxSample");
        Scene scene = new Scene(new Group(), 450, 250);
        
        final ComboBox emailComboBox = new ComboBox();
        emailComboBox.getItems().addAll(
            "jacob.smith@example.com",
            "isabella.johnson@example.com",
            "ethan.williams@example.com",
            "emma.jones@example.com",
            "michael.brown@example.com"  
        );
        emailComboBox.setPromptText("Email address");
        emailComboBox.setEditable(true);        
        emailComboBox.valueProperty().addListener(new ChangeListener<String>() {
            @Override public void changed(ObservableValue ov, String t, String t1) {                
                address = t1;                
            }    
        });
        
        final ComboBox priorityComboBox = new ComboBox();
        priorityComboBox.getItems().addAll(
            "Highest",
            "High",
            "Normal",
            "Low",
            "Lowest" 
        );   

        priorityComboBox.setValue("Normal");
        priorityComboBox.setCellFactory(
            new Callback<ListView<String>, ListCell<String>>() {
                @Override public ListCell<String> call(ListView<String> param) {
                    final ListCell<String> cell = new ListCell<String>() {
                        {
                            super.setPrefWidth(100);
                        }    
                        @Override public void updateItem(String item, 
                            boolean empty) {
                                super.updateItem(item, empty);
                                if (item != null) {
                                    setText(item);    
                                    if (item.contains("High")) {
                                        setTextFill(Color.RED);
                                    }
                                    else if (item.contains("Low")){
                                        setTextFill(Color.GREEN);
                                    }
                                    else {
                                        setTextFill(Color.BLACK);
                                    }
                                }
                                else {
                                    setText(null);
                                }
                            }
                };
                return cell;
            }
        });
     
        
        button.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent e) {
                if (emailComboBox.getValue() != null && 
                    !emailComboBox.getValue().toString().isEmpty()){
                        notification.setText("Your message was successfully sent"
                            + " to " + address);   
                        emailComboBox.setValue(null);
                        if (priorityComboBox.getValue() != null && 
                            !priorityComboBox.getValue().toString().isEmpty()){
                                priorityComboBox.setValue(null);
                            }
                        subject.clear();
                        text.clear();
                }
                else {
                    notification.setText("You have not selected a recipient!"); 
                }
            }
        });
        
        GridPane grid = new GridPane();
        grid.setVgap(4);
        grid.setHgap(10);
        grid.setPadding(new Insets(5, 5, 5, 5));
        grid.add(new Label("To: "), 0, 0);
        grid.add(emailComboBox, 1, 0);
        grid.add(new Label("Priority: "), 2, 0);
        grid.add(priorityComboBox, 3, 0);
        grid.add(new Label("Subject: "), 0, 1);
        grid.add(subject, 1, 1, 3, 1);            
        grid.add(text, 0, 2, 4, 1);
        grid.add(button, 0, 3);
        grid.add (notification, 1, 3, 3, 1);
        
        Group root = (Group)scene.getRoot();
        root.getChildren().add(grid);
        stage.setScene(scene);
        stage.show();
 
    }    
}