JavaFX TextField.setOnKeyPressed bahavior change in Ubuntu 18.04

I noticed that JavaFX behaves differently after updated to Ubuntu 18.04. I have a little program to illustrate this issue:

package sample;

import javafx.application.Application;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.control.TextField;
import javafx.stage.Stage;

public class Main extends Application {

    @Override
    public void start(Stage primaryStage) throws Exception{
        primaryStage.setTitle("Key Pressed");
        Group root = new Group();
        Scene scene = new Scene(root, 300, 275);
        TextField textField = new TextField();
        textField.setOnKeyPressed(e -> System.out.println("KeyPressed: " + textField.getText()));
        textField.setOnKeyReleased(e -> System.out.println("KeyReleased: " + textField.getText()));
        root.getChildren().add(textField);
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }
}

I compiled this program and run on ubuntu 16.04 Oracle java 1.8.0_152, ubuntu 18.04 java 1.8.0_152, ubuntu 18.04 java 1.8.0_192, Windows 10 java 1.8.0_161, and typing 'abcd' (without quotes) into the textfield.

When I run it on ubuntu 16.04 and Windows 10, the output is

KeyPressed: 
KeyReleased: a
KeyPressed: a
KeyReleased: ab
KeyPressed: ab
KeyReleased: abc
KeyPressed: abc
KeyReleased: abcd

But when I run the program on ubuntu 18.04, the output is

KeyReleased: a
KeyReleased: ab
KeyReleased: abc
KeyReleased: abcd

Why the difference of same java program on different OS (even with same version of jre)? Which is the correct behavior?