建造者模式

建造者模式的主要特征是，通过一步一步的方式生成一些东西。每个生成的东西，即使其中的任何一步都不相同，但也将遵循同样的过程。

4个角色：指挥者(Director)，建造者(Builder)，具体建造者(ConcreteBuilder)，产品(Product)

产品：需要创建的对象产品

建造者：本质为抽象类，里面的抽象方法供具体建造者重写，声明产品的引用

具体建造者：创建产品的实例并且实现建造者多个方法对产品进行装配

指挥者：调用建造者抽象类以及其方法

代码：

 

// produce to be built

 

class Starbucks {

 

    private String size;

 

    private String drink;

 

  

 

    public void setSize(String size) {

 

        this.size = size;

 

    }

 

  

 

    public void setDrink(String drink) {

 

        this.drink = drink;

 

    }

 

}

 

  

 

//abstract builder

 

abstract class StarbucksBuilder {

 

    protected Starbucks starbucks;

 

  

 

    public Starbucks getStarbucks() {

 

        return starbucks;

 

    }

 

  

 

    public void createStarbucks() {

 

        starbucks = new Starbucks();

 

        System.out.println("a drink is created");

 

    }

 

  

 

    public abstract void buildSize();

 

    public abstract void buildDrink();

 

}

 

  

 

// Concrete Builder to build tea

 

class TeaBuilder extends StarbucksBuilder {

 

    public void buildSize() {

 

        starbucks.setSize("large");

 

        System.out.println("build large size");

 

    }

 

  

 

    public void buildDrink() {

 

        starbucks.setDrink("tea");

 

        System.out.println("build tea");

 

    }

 

  

 

}

 

  

 

// Concrete builder to build coffee

 

class CoffeeBuilder extends StarbucksBuilder {

 

    public void buildSize() {

 

        starbucks.setSize("medium");

 

        System.out.println("build medium size");

 

    }

 

  

 

    public void buildDrink() {

 

        starbucks.setDrink("coffee");

 

        System.out.println("build coffee");

 

    }

 

}

 

  

 

//director to encapsulate the builder

 

class Waiter {

 

    private StarbucksBuilder starbucksBuilder;

 

  

 

    public void setStarbucksBuilder(StarbucksBuilder builder) {

 

        starbucksBuilder = builder;

 

    }

 

  

 

    public Starbucks getstarbucksDrink() {

 

        return starbucksBuilder.getStarbucks();

 

    }

 

  

 

    public void constructStarbucks() {

 

        starbucksBuilder.createStarbucks();

 

        starbucksBuilder.buildDrink();

 

        starbucksBuilder.buildSize();

 

    }

 

}

 

  

 

//customer

 

public class Customer {

 

    public static void main(String[] args) {

 

        Waiter waiter = new Waiter();

 

        StarbucksBuilder coffeeBuilder = new CoffeeBuilder();

 

  

 

        //Alternatively you can use tea builder to build a tea

 

        //StarbucksBuilder teaBuilder = new TeaBuilder();

 

  

 

        waiter.setStarbucksBuilder(coffeeBuilder);

 

        waiter.constructStarbucks();

 

  

 

        //get the drink built

 

        Starbucks drink = waiter.getstarbucksDrink();

 

  

 

    }

 

}