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();
}
}
