java design pattern - Template pattern

Template pattern 是很容易理解的，父类只声明一些函数，并不去实现，具体的实现让子类去自己实现。

Usage in jdk: 
All non-abstract methods of java.io.InputStream, java.io.OutputStream, java.io.Reader and java.io.Writer 。 

package template;

abstract class PurchaseOrderTemplate{
    public abstract void doSelect();
    public abstract void doPayment();

    public final void doPack(){
        System.out.println("Gift wrap done");
    }

    public abstract void doDelivery();

    public final void processOrder(){
        doSelect();
        doPayment();
        doPack();
        doDelivery();
    }
}

class StorePurchaseOrder extends PurchaseOrderTemplate{
    @Override
    public void doSelect(){
        System.out.println("Customer chooses the item from shelf");
    }

    @Override
    public void doPayment(){
        System.out.println("Pays at counter through cash/POS");
    }

    @Override
    public void doDelivery(){
        System.out.println("Item delivered to in delivery counter");
    }
}

class OnlinePurchaseOrder extends PurchaseOrderTemplate{
    @Override
    public void doSelect(){
        System.out.println("Item added to online shopping cart");
        System.out.println("Get gift wrap preference.");
        System.out.println("Get delivery address");
    }

    @Override
    public void doPayment(){
        System.out.println("Online payment through Netbanking/Cards");
    }

    @Override
    public void doDelivery(){
        System.out.println("Ship the item through post to delivery address");
    }
}


public class TemplatePatternDemo {
    public static void main(String[] args){
        PurchaseOrderTemplate online = new OnlinePurchaseOrder();
        online.processOrder();
        PurchaseOrderTemplate offline = new StorePurchaseOrder();
        offline.processOrder();
    }
}