Abstract Factory

Abstract Factory is a creational pattern that provides an interface for creating families of related or dependent objects without specifying their concrete classes. Think of it as a factory of factories — you pick a factory, and all objects you create through it are guaranteed to be compatible with each other.

You're building a cross-platform UI toolkit. You have Button and Checkbox widgets. Each platform (Windows, macOS, Linux) needs its own look-and-feel. You need to guarantee that if you create a WindowsButton, you also create a WindowsCheckbox — never a mixed family like WindowsButton + MacCheckbox.

interface Button {
    void render();
    void onClick();
}

interface Checkbox {
    void render();
    void toggle();
}

// javax.xml.parsers.DocumentBuilderFactory

DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();

DocumentBuilder builder = factory.newDocumentBuilder();

// javax.xml.transform.TransformerFactory — same pattern

TransformerFactory tf = TransformerFactory.newInstance();

Transformer transformer = tf.newTransformer();