patterns10FacadePattern

1package pkg8patterns;2 3/*4 * Facade (Structural)5 * -------------------6 * INTENT: provide a single, simplified interface to a complex subsystem.7 * UML: Facade --> {SubsystemA, SubsystemB, SubsystemC}.8 * PROS: reduces coupling; easier to use; hides complexity.9 * CONS: can become a god object if it grows unchecked.10 * REAL-WORLD: javax.faces, JOptionPane, a "service" wrapping repositories.11 */12public class patterns10FacadePattern {13 14    // Complex subsystem15    static class Cpu { String freeze() { return "CPU freeze"; } String execute() { return "CPU execute"; } }16    static class Memory { String load(String data) { return "Memory load(" + data + ")"; } }17    static class HardDrive { String read() { return "HardDrive read boot sector"; } }18 19    // Facade exposes a simple operation20    static class Computer {21        private final Cpu cpu = new Cpu();22        private final Memory memory = new Memory();23        private final HardDrive disk = new HardDrive();24        void start() {25            System.out.println(cpu.freeze());26            System.out.println(memory.load(disk.read()));27            System.out.println(cpu.execute());28            System.out.println("Computer started.");29        }30    }31 32    public static void main(String[] args) {33        new Computer().start();   // client uses one simple call34    }35}