Buttons fire action events when they are activated (e.g. clicked, a keybinding for the button is pressed, ...).

button.setOnAction(new EventHandler<ActionEvent>() {
    @Override
    public void handle(ActionEvent event) {
        System.out.println("Hello World!");
    }
});

If you are using Java 8+, you can use lambdas for action listeners.

button.setOnAction((ActionEvent a) -> System.out.println("Hello, World!"));
// or
button.setOnAction(a -> System.out.println("Hello, World!"));

Buttons can have a graphic. graphic can be any JavaFX node, like a ProgressBar

button.setGraphic(new ProgressBar(-1));

An ImageView

button.setGraphic(new ImageView("images/icon.png"));

Or even another button

button.setGraphic(new Button("Nested button"));

Creation of a Button is simple:

Button sampleButton = new Button();

This will create a new Button without any text or graphic inside.

If you want to create a Button with a text, simply use the constructor that takes a String as parameter (which sets the textProperty of the Button):

Button sampleButton = new Button("Click Me!");

If you want to create a Button with a graphic inside or any other Node, use this constructor:

Button sampleButton = new Button("I have an icon", new ImageView(new Image("icon.png")));

Button API provides an easy way to assign common keyboard shortcuts to buttons without the need to access accelerators' list assigned to Scene or explicitly listening to the key events. Namely, two convenience methods are provided: setDefaultButton and setCancelButton:

• Setting setDefaultButton to true will cause the Button to fire every time it receives a KeyCode.ENTER event.

• Setting setCancelButton to true will cause the Button to fire every time it receives a KeyCode.ESCAPE event.

The following example creates a Scene with two buttons that are fired when enter or escape keys are pressed, regardless whether they are focused or not.

FlowPane root = new FlowPane();
        
Button okButton = new Button("OK");
okButton.setDefaultButton(true);
okButton.setOnAction(e -> {
    System.out.println("OK clicked.");
});
        
Button cancelButton = new Button("Cancel");            
cancelButton.setCancelButton(true);
cancelButton.setOnAction(e -> {
    System.out.println("Cancel clicked.");
});
        
root.getChildren().addAll(okButton, cancelButton);
Scene scene = new Scene(root);

The code above will not work if these KeyEvents are consumed by any parent Node:

scene.setOnKeyPressed(e -> {
    e.consume();
});