Design Patterns in Java

abstract-factory-pattern.java

// ingredients: dough, sauce
public interface Dough {};
public interface Cheese {};
public interface Pepperoni {};

public class ThinCrustDough implements Dough {
    public String toString() { return "This Crust Dough"; }
}

public class ParmesanCheese implements Cheese {
    public String toString() { return "Shredded Parmesan"; }
}

public class SlicedPepperoni implements Pepperoni {
    public String toString() { return "Sliced Pepperoni"; }
}

// abstract ingredient factory
public interface PizzaIngredientFactory {
    public Dough createDough();
    public Cheese createCheese();
    public Pepperoni createPepperoni();
}

public class NYPizzaIngredientFactory implements PizzaIngredientFactory {
    public Dough createDough() { return new ThinCrustDough(); }
    public Sauce createCheese() { return new ParmesanCheese(); }
    public Pepperoni createPepperoni() { return new SlicedPepperoni(); }
}

//The Product classes
public abstract class Pizza {
    String name;
    String dough;
    String cheese;
    String pepperoni;
    
    public void setName(String name) { this.name = name; }
    public String getName() { return name; }
    abstract void prepare();
    public void bake() { System.out.println("Baking " + name); }
    
    public String toString() {
        StringBuffer sb = new StringBuffer();
        sb.append(name + ": ");
        if (dough != null) sb.append(dough + " ");
        if (cheese != null) sb.append(cheese + " ");
        if (pepperoni != null) sb.append(pepperoni + " ");
        return sb.toString();
    }
}

public class CheesePizza extends Pizza {
    PizzaIngredientFactory ingredientFactory;
    public CheesePizza(PizzaIngredientFactory ingredientFactory) {
        this.ingredientFactory = ingredientFactory;
    }
    
    void prepare() {
        System.out.println("Preparing " + name);
        dough = ingredientFactory.createDough();
        cheese = ingredientFactory.createCheese();
    }
}

public class PepperoniPizza extends Pizza {
    PizzaIngredientFactory ingredientFactory;
    
    public PepperoniPizza(PizzaIngredientFactory ingredientFactory) {
        this.ingredientFactory = ingredientFactory;
    }
    
    void prepare() {
        System.out.println("Preparing " + name);
        dough = ingredientFactory.createDough();
        cheese = ingredientFactory.createCheese();
        pepperoni = ingredientFactory.createPepperoni();
    }
}

// Client code
public abstract class PizzaStore {
    public Pizza orderPizza(String type) {
        Pizza pizza = createPizza(type);
        pizza.prepare();
        pizza.bake();
        return pizza;
    }

    // A factory method handles object creation and encapsulates it in a subclass
    protected abstract Pizza createPizza(String type);
}

public class NYPizzaStore extends PizzaStore {
    protected Pizza createPizza(String type) {
        Pizza pizza = null;
        PizzaIngredientFactory ingredientFactory = new NYPizzaIngredientFactory();
        
        if (item.equalsIgnoreCase("cheese")) {
            pizza = new CheesePizza(ingredientFactory);
            pizza.setName("New York Style Cheese Pizza");
        } else if (item.equalsIgnoreCase("pepperoni")) {
            pizza = new PepperoniPizza(ingredientFactory);
            pizza.setName("New York Style Pepperoni Pizza");
        }
        return pizza;
    }
}

factory-method-pattern.java

//The Product classes
public abstract class Pizza {
    String name;
    
    public String getName() { return name; }
    public void prepare() { System.out.println("Preparing " + name); }
    public void bake() { System.out.println("Baking " + name); }
}

public class NYStyleCheesePizza extends Pizza {
    public NYStyleCheesePizza() {
        name = "NY Style Cheese Pizza";
    }
}

public class NYStyleVeggiePizza extends Pizza {
    public NYStyleVeggiePizza() {
        name = "NY Style Veggie Pizza";
    }
}

//The Creator classes
public abstract class PizzaStore {
    public Pizza orderPizza(String type) {
        Pizza pizza = createPizza(type);
        pizza.prepare();
        pizza.bake();
        return pizza;
    }

    // A factory method handles object creation and encapsulates it in a subclass
    protected abstract Pizza createPizza(String type);
}

public class NYPizzaStore extends PizzaStore {
    Pizza createPizza(String type) {
        Pizza pizza = null;
        if (type.equalsIgnoreCase("cheese")) {
            pizza = new NYStyleCheesePizza();
        } else if (type.equalsIgnoreCase("veggie")) {
            pizza = new NYStyleVeggiePizza();
        }
        return pizza;
    }
}

factory-pattern.java

public abstract class Pizza {
    String name;
    
    public String getName() { return name; }
    public void prepare() { System.out.println("Preparing " + name); }
    public void bake() { System.out.println("Baking " + name); }
}
 
public class CheesePizza extends Pizza {
    public CheesePizza() { name = "CheesePizza"; }
}
 
public class VeggiePizza extends Pizza {
    public VeggiePizza() { name = "VeggiePizza"; }
}
 
public class PizzaFactory {
    public Pizza createPizza(String type) {
        Pizza pizza = null;
        if (type.equalsIgnoreCase("cheese")) {
            pizza = new CheesePizza();
        } else if (type.equalsIgnoreCase("veggie")) {
            pizza = new VeggiePizza();
        }
        return pizza;
    }
}

// Factory client code
public class PizzaStore {
    PizzaFactory factory;
    
    public PizzaStore(PizzaFactory factory) {
        this.factory = factory;
    }
    
    public Pizza orderPizza(String type) {
        Pizza pizza = factory.createPizza(type);
        pizza.prepare();
        pizza.bake();
        return pizza;
    }
}