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();

  

    }

}