Start small

Zero helps you make Java apps and games. Start with one of the two tracks below. Use ordinary Java fields, methods and objects to hold your app's state. You can learn more JavaFX when your project needs it.

The starter opens with a small quiz. Keep it while you learn, or follow an example's copy instructions to replace it in a separate starter folder. Examples are outside src/ until you copy them. If an older downloaded kit does not include these examples, the website's example pages show the complete files to copy into the same starter destinations.

Choose SimpleApp for a quiz, calculator, study tool or small form. Start with the complete Hello app, including its stylesheet.

launch → settings() → setup() → show the window
                                    ↓
                         respond to user events

Override settings() once to call size(width, height) and title("My app"). Override setup() once to create controls, connect handlers and call show(screen). Keep the example's main method to launch the app. There is no automatic update() or draw() callback in SimpleApp.

Start with these ordinary JavaFX classes:

Class	Use	First methods to learn
Label	Show instructions or feedback	setText("Hello")
Button	Let the user choose an action	setOnAction(event -> { ... }), setText("Play")
TextField	Read a short answer	getText(), setText(""), setPromptText("Your name")
VBox	Arrange controls vertically	new VBox(16, heading, instructions, name, actions, feedback)
HBox	Arrange controls horizontally	new HBox(12, hello, reset)

Import controls from javafx.scene.control and layouts from javafx.scene.layout. A box constructor's first number is the spacing between its children. You can also call setSpacing(12) later. Use setPadding(new Insets(24)) for space inside the edge of a box, and setAlignment(Pos.CENTER_LEFT) to align its children. Import Insets and Pos from javafx.geometry.

An event handler runs when the user takes an action:

hello.setOnAction(event -> {
    String enteredName = name.getText().trim();
    if (enteredName.isEmpty()) {
        feedback.setText("Type your name first.");
    } else {
        feedback.setText("Hello, " + enteredName + "!");
    }
});

name, hello and feedback are the controls created in setup. JavaFX redraws them after their values change. If an action should become unavailable, use hello.setDisable(true); use false to enable it again. Hello app puts the greeting logic in greet() and calls that ordinary method from its handlers.

Try three changes in Hello app: change the greeting, change the main button colour, then change the VBox spacing. Use the appearance guide to change its colours and spacing.

Choose SketchApp for a drawing, moving objects or a small game. Start with the complete Reach the coin game.

launch → settings() → create canvas → setup() → show the window
                                                    ↓
                                  update(seconds) → draw()
                                         ↑             │
                                         └─────────────┘

Use settings() for size(...) and title(...), and setup() to create your objects. Each frame, update(seconds) changes positions and checks the rules; draw() displays the current state. Zero calls these methods on Main.

Start with this small drawing and input set:

Method	Use
background(Color.WHITE)	Clear the canvas for a fresh frame
fill(Color.BLUE)	Choose the colour for filled shapes and text
rect(x, y, width, height)	Draw a filled rectangle
circle(centreX, centreY, diameter)	Draw a filled circle
textSize(20)	Choose the default font at this size
text("Hello", x, y)	Draw text; y is its baseline
keyDown(KeyCode.RIGHT)	Check whether a key is held
mouseX(), mouseY()	Read the tracked canvas pointer position
mouseDown(MouseButton.PRIMARY)	Check whether the mouse button is held
width(), height()	Read the canvas dimensions

Import Color from javafx.scene.paint, and KeyCode and MouseButton from javafx.scene.input. Canvas coordinates start at (0, 0) in the top left; x increases to the right and y increases downward.

Click the canvas before using game keys. Returning from another window may require another click. Typing in a text control belongs to that control. Input methods report held state, so holding R in Reach the coin keeps resetting until you release it.

Move using elapsed time rather than a fixed distance per frame:

if (keyDown(KeyCode.RIGHT)) {
    x += 180 * seconds; // 180 pixels per second
}

Frame rate can vary. The first frame receives 0 seconds and later elapsed values are capped at 0.1 seconds. The canvas has the fixed pixel dimensions chosen in settings; resizing the window does not scale the drawing.

Your objects are ordinary Java objects. Main must call their methods explicitly:

// Inside Main.update:
player.update(horizontal, vertical, seconds, width(), height());

// Inside Main.draw, after drawing the background and coin:
player.draw(this);

Zero never discovers Player or updates it automatically. In Reach the coin, Main owns the win flag and Player owns its position and movement methods. Follow the game's two tiny changes, then try changing its colours.

Keep event handlers and frame methods short: they share the JavaFX UI thread. Let callbacks return so JavaFX can handle input and display the next frame.

The appearance guide introduces fonts, stylesheets and images. The full Zero API reference covers outlines, lines, images and native JavaFX access through graphics(), canvas() and layout(). These are available when your project needs them. Wider JavaFX controls and layouts remain ordinary JavaFX APIs; learning them does not require a new Zero engine or object model.