Factory Method Pattern(工廠模式)

• Definition

The Factory Method Pattern defines an interface for creating an object, but lets subclasses decide which class to instantiate. Factory Method lets a class defer instantiation to subclasses.

• Class Diagram

• Product Role

public abstract class Product {
    public void method1() {
    //doSomething
    }

public abstract void method2() ;

}

• ConcreteProduct Role

public ConcreteProduct1 extend Product {
    public void method2() {
        //doSomething
    }
}

public ConcreteProduct2 extend Product {
    public void method2() {
        //doSomething
    }
}

• Creator Role

public abstract class Creator {
    public abstract <T extends Product> T createProduct(Class<T> c);
}

• ConcreteCreator Role

public class ConcreteCreator extends Creator {
    public <T extends Product> T createProduct(Class<T> c) {
        Product product=null;
        try {
            product = (Product)Class.forName(c.getName()).newInstance();
        } catch (Exception e) {
            //error process
        }
        Return (T)product;
    }
}

• Client Role

public class Client {
    public static void main(String[] args) {
        Creator creator = new ConcreteCreator();
        Product product = creator.creatorProduct(ConcreteProduct1.class);
        //doSomething
    }
}

Decorator Pattern(裝飾模式)

• Definition

The Decorator Pattern attaches additional responsibilities to an object dynamically. Decorators provide a flexible alternative to subclassing for extending functionality.

• Class Diagram

• Component Role

public abstract class Component {
    public abstract void operate();
}

• ConcreteComponent Role

public class ConcreteComponent extends Component {
    @Override
    public void operate() {
        System.out.println("do Something");
    }
}

• Decorator Role

public abstract class Decorator extends Component {
    private Component _component;
    
    public Decorator(Component component) {
        this._component = component;
    }

    @Override
    public void operate() {
        this._component.operate();
    }
}

• ConcreteDecorator Role

public class ConcreteDecorator1 extends Decorator {

    public ConcreteDecorator1(Component component)
        super(component);
    }

    private void method1() {
        System.out.println("method1 Decorator");
    }

    public void operate() {    
        this.method1();
        super.operate();
    }
}

public class ConcreteDecorator2 extends Decorator {

    public ConcreteDecorator2(Component component)
        super(component);
    }

    private void method2() {
        System.out.println("method2 Decorator");
    }

    public void operate() {    
        this.method2();
        super.operate();
    }
}

• Client Role

public class Client {
    public static void main(String[] args) {
        Component component = new ConcreteComponent();
        component = new ConcreteDecorator1(component);
         component = new ConcreteDecorator2(component);
        component.operate();
    }
}