Add creational patterns, Interpreter; remove scripts; update README

01-creational/abstract-factory/Application.java

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+package abstractfactory;
+
+/** Client - uses the factory without knowing concrete classes */
+public class Application {
+    private final Button button;
+    private final Checkbox checkbox;
+
+    public Application(GUIFactory factory) {
+        button   = factory.createButton();
+        checkbox = factory.createCheckbox();
+    }
+
+    public void render() {
+        button.render();
+        checkbox.render();
+    }
+
+    public void simulateClick() {
+        button.onClick();
+    }
+}

01-creational/abstract-factory/Button.java

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+package abstractfactory;
+
+public interface Button {
+    void render();
+    void onClick();
+}

01-creational/abstract-factory/Checkbox.java

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+package abstractfactory;
+
+public interface Checkbox {
+    void render();
+}

01-creational/abstract-factory/GUIFactory.java

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+package abstractfactory;
+
+/** Abstract Factory - creates families of related UI components */
+public interface GUIFactory {
+    Button createButton();
+    Checkbox createCheckbox();
+}

01-creational/abstract-factory/MacButton.java

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+package abstractfactory;
+
+public class MacButton implements Button {
+    @Override public void render()   { System.out.println("[Mac] Rendering button with rounded corners"); }
+    @Override public void onClick()  { System.out.println("[Mac] Button clicked - glow animation"); }
+}

01-creational/abstract-factory/MacCheckbox.java

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+package abstractfactory;
+
+public class MacCheckbox implements Checkbox {
+    @Override public void render() { System.out.println("[Mac] Rendering checkbox with rounded tick box"); }
+}

01-creational/abstract-factory/MacFactory.java

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+package abstractfactory;
+
+public class MacFactory implements GUIFactory {
+    @Override public Button   createButton()   { return new MacButton(); }
+    @Override public Checkbox createCheckbox() { return new MacCheckbox(); }
+}

01-creational/abstract-factory/Main.java

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+package abstractfactory;
+
+public class Main {
+    public static void main(String[] args) {
+        System.out.println("=== Abstract Factory Pattern Demo ===\n");
+
+        String os = System.getProperty("os.name", "Windows").toLowerCase();
+        GUIFactory factory = os.contains("mac") ? new MacFactory() : new WindowsFactory();
+
+        System.out.println("Detected OS family: " + (os.contains("mac") ? "Mac" : "Windows"));
+        System.out.println();
+
+        Application app = new Application(factory);
+        app.render();
+        app.simulateClick();
+
+        System.out.println("\n--- Forcing Mac UI ---");
+        Application macApp = new Application(new MacFactory());
+        macApp.render();
+        macApp.simulateClick();
+    }
+}

01-creational/abstract-factory/WindowsButton.java

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+package abstractfactory;
+
+public class WindowsButton implements Button {
+    @Override public void render()   { System.out.println("[Windows] Rendering button with square corners"); }
+    @Override public void onClick()  { System.out.println("[Windows] Button clicked - raised border effect"); }
+}

01-creational/abstract-factory/WindowsCheckbox.java

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+package abstractfactory;
+
+public class WindowsCheckbox implements Checkbox {
+    @Override public void render() { System.out.println("[Windows] Rendering checkbox with square tick box"); }
+}

01-creational/abstract-factory/WindowsFactory.java

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+package abstractfactory;
+
+public class WindowsFactory implements GUIFactory {
+    @Override public Button   createButton()   { return new WindowsButton(); }
+    @Override public Checkbox createCheckbox() { return new WindowsCheckbox(); }
+}

01-creational/builder/Director.java

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+package builder;
+
+/** Director knows how to build common configurations */
+public class Director {
+    public House buildStarter(House.Builder builder) {
+        return builder.rooms(2).floors(1).garage(false).roofType("gabled").build();
+    }
+
+    public House buildLuxury(House.Builder builder) {
+        return builder.rooms(6).floors(3).garage(true).garden(true).pool(true).roofType("hip").build();
+    }
+}

01-creational/builder/House.java

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+package builder;
+
+public class House {
+    private final int rooms;
+    private final int floors;
+    private final boolean hasGarage;
+    private final boolean hasGarden;
+    private final boolean hasPool;
+    private final String roofType;
+
+    private House(Builder builder) {
+        this.rooms     = builder.rooms;
+        this.floors    = builder.floors;
+        this.hasGarage = builder.hasGarage;
+        this.hasGarden = builder.hasGarden;
+        this.hasPool   = builder.hasPool;
+        this.roofType  = builder.roofType;
+    }
+
+    @Override
+    public String toString() {
+        return "House{rooms=" + rooms + ", floors=" + floors
+                + ", garage=" + hasGarage + ", garden=" + hasGarden
+                + ", pool=" + hasPool + ", roof='" + roofType + "'}";
+    }
+
+    public static class Builder {
+        private int rooms = 1;
+        private int floors = 1;
+        private boolean hasGarage = false;
+        private boolean hasGarden = false;
+        private boolean hasPool   = false;
+        private String roofType   = "flat";
+
+        public Builder rooms(int rooms)           { this.rooms = rooms;         return this; }
+        public Builder floors(int floors)         { this.floors = floors;       return this; }
+        public Builder garage(boolean v)          { this.hasGarage = v;         return this; }
+        public Builder garden(boolean v)          { this.hasGarden = v;         return this; }
+        public Builder pool(boolean v)            { this.hasPool = v;           return this; }
+        public Builder roofType(String roofType)  { this.roofType = roofType;   return this; }
+        public House build()                      { return new House(this); }
+    }
+}

01-creational/builder/Main.java

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+package builder;
+
+public class Main {
+    public static void main(String[] args) {
+        System.out.println("=== Builder Pattern Demo ===\n");
+
+        Director director = new Director();
+
+        House starter = director.buildStarter(new House.Builder());
+        System.out.println("Starter home : " + starter);
+
+        House luxury = director.buildLuxury(new House.Builder());
+        System.out.println("Luxury home  : " + luxury);
+
+        // Client builds a custom house directly without the Director
+        House custom = new House.Builder()
+                .rooms(4).floors(2).garden(true).roofType("mansard").build();
+        System.out.println("Custom home  : " + custom);
+    }
+}

01-creational/factory-method/EmailNotification.java

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+package factorymethod;
+
+public class EmailNotification implements Notification {
+    private final String email;
+    public EmailNotification(String email) { this.email = email; }
+
+    @Override
+    public void send(String message) {
+        System.out.println("Email -> " + email + ": " + message);
+    }
+}

01-creational/factory-method/EmailService.java

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+package factorymethod;
+
+public class EmailService extends NotificationService {
+    private final String email;
+    public EmailService(String email) { this.email = email; }
+
+    @Override
+    protected Notification createNotification() {
+        return new EmailNotification(email);
+    }
+}

01-creational/factory-method/Main.java

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+package factorymethod;
+
+public class Main {
+    public static void main(String[] args) {
+        System.out.println("=== Factory Method Pattern Demo ===\n");
+
+        NotificationService[] services = {
+            new EmailService("alice@example.com"),
+            new SmsService("+1-555-0123"),
+            new PushService("device-token-abc123")
+        };
+
+        for (NotificationService service : services) {
+            service.notifyUser("Your order #1042 has been shipped!");
+        }
+    }
+}

01-creational/factory-method/Notification.java

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+package factorymethod;
+
+public interface Notification {
+    void send(String message);
+}

01-creational/factory-method/NotificationService.java

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+package factorymethod;
+
+/** Creator - declares the factory method */
+public abstract class NotificationService {
+    protected abstract Notification createNotification();
+
+    public void notifyUser(String message) {
+        Notification n = createNotification();
+        n.send(message);
+    }
+}

01-creational/factory-method/PushNotification.java

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+package factorymethod;
+
+public class PushNotification implements Notification {
+    private final String deviceToken;
+    public PushNotification(String deviceToken) { this.deviceToken = deviceToken; }
+
+    @Override
+    public void send(String message) {
+        System.out.println("Push -> " + deviceToken + ": " + message);
+    }
+}

01-creational/factory-method/PushService.java

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+package factorymethod;
+
+public class PushService extends NotificationService {
+    private final String token;
+    public PushService(String token) { this.token = token; }
+
+    @Override
+    protected Notification createNotification() {
+        return new PushNotification(token);
+    }
+}

01-creational/factory-method/SmsNotification.java

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+package factorymethod;
+
+public class SmsNotification implements Notification {
+    private final String phone;
+    public SmsNotification(String phone) { this.phone = phone; }
+
+    @Override
+    public void send(String message) {
+        System.out.println("SMS -> " + phone + ": " + message);
+    }
+}

01-creational/factory-method/SmsService.java

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+package factorymethod;
+
+public class SmsService extends NotificationService {
+    private final String phone;
+    public SmsService(String phone) { this.phone = phone; }
+
+    @Override
+    protected Notification createNotification() {
+        return new SmsNotification(phone);
+    }
+}

01-creational/prototype/Circle.java

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+package prototype;
+
+public class Circle extends Shape {
+    private int radius;
+
+    public Circle(int radius, String color) {
+        this.radius = radius;
+        this.color  = color;
+    }
+
+    /** Copy constructor used by clone() */
+    private Circle(Circle source) {
+        super(source);
+        this.radius = source.radius;
+    }
+
+    @Override
+    public Circle clone() { return new Circle(this); }
+
+    @Override
+    public String toString() {
+        return "Circle{color=" + color + ", radius=" + radius + ", pos=(" + x + "," + y + ")}";
+    }
+}

01-creational/prototype/Main.java

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+package prototype;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class Main {
+    public static void main(String[] args) {
+        System.out.println("=== Prototype Pattern Demo ===\n");
+
+        List<Shape> originals = new ArrayList<>();
+        originals.add(new Circle(10, "red"));
+        originals.add(new Rectangle(20, 30, "blue"));
+
+        // Clone each shape - no need to know the concrete type
+        List<Shape> copies = new ArrayList<>();
+        for (Shape shape : originals) {
+            copies.add(shape.clone());
+        }
+
+        // Mutate copies - originals are unaffected
+        copies.get(0).setColor("green");
+        copies.get(0).move(5, 5);
+        copies.get(1).setColor("yellow");
+
+        System.out.println("--- Originals ---");
+        originals.forEach(System.out::println);
+
+        System.out.println("\n--- Clones (mutated) ---");
+        copies.forEach(System.out::println);
+
+        System.out.println("\nSame instance? " + (originals.get(0) == copies.get(0)));
+    }
+}

01-creational/prototype/Rectangle.java

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+package prototype;
+
+public class Rectangle extends Shape {
+    private int width;
+    private int height;
+
+    public Rectangle(int width, int height, String color) {
+        this.width  = width;
+        this.height = height;
+        this.color  = color;
+    }
+
+    private Rectangle(Rectangle source) {
+        super(source);
+        this.width  = source.width;
+        this.height = source.height;
+    }
+
+    @Override
+    public Rectangle clone() { return new Rectangle(this); }
+
+    @Override
+    public String toString() {
+        return "Rectangle{color=" + color + ", size=" + width + "x" + height + ", pos=(" + x + "," + y + ")}";
+    }
+}

01-creational/prototype/Shape.java

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+package prototype;
+
+/** Prototype - every shape can clone itself */
+public abstract class Shape {
+    protected String color;
+    protected int x;
+    protected int y;
+
+    protected Shape(Shape source) {
+        this.color = source.color;
+        this.x     = source.x;
+        this.y     = source.y;
+    }
+
+    protected Shape() {}
+
+    public abstract Shape clone();
+
+    public void setColor(String color) { this.color = color; }
+    public String getColor()           { return color; }
+    public void move(int x, int y)     { this.x = x; this.y = y; }
+}

01-creational/singleton/DatabaseConnection.java

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+package singleton;
+
+/**
+ * Thread-safe Singleton using double-checked locking.
+ */
+public class DatabaseConnection {
+    private static volatile DatabaseConnection instance;
+    private final String url;
+    private int queryCount = 0;
+
+    private DatabaseConnection() {
+        this.url = "jdbc:mysql://localhost:3306/myapp";
+        System.out.println("Establishing connection to " + url);
+    }
+
+    public static DatabaseConnection getInstance() {
+        if (instance == null) {
+            synchronized (DatabaseConnection.class) {
+                if (instance == null) {
+                    instance = new DatabaseConnection();
+                }
+            }
+        }
+        return instance;
+    }
+
+    public String executeQuery(String sql) {
+        queryCount++;
+        return "Result #" + queryCount + " for: " + sql;
+    }
+
+    public int getQueryCount() { return queryCount; }
+    public String getUrl()     { return url; }
+}

01-creational/singleton/Main.java

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+package singleton;
+
+public class Main {
+    public static void main(String[] args) {
+        System.out.println("=== Singleton Pattern Demo ===\n");
+
+        DatabaseConnection c1 = DatabaseConnection.getInstance();
+        DatabaseConnection c2 = DatabaseConnection.getInstance();
+        DatabaseConnection c3 = DatabaseConnection.getInstance();
+
+        System.out.println("\nAll three references same instance? " + (c1 == c2 && c2 == c3));
+
+        System.out.println(c1.executeQuery("SELECT * FROM users"));
+        System.out.println(c2.executeQuery("SELECT * FROM orders"));
+        System.out.println(c3.executeQuery("SELECT COUNT(*) FROM products"));
+
+        System.out.println("\nTotal queries: " + c1.getQueryCount());
+    }
+}