生成器模式

生成器模式也称为建造者模式，将一个复杂对象的构建与表示分离，使得同样的构建过程可以创建不同的表示（Builder）

生成器模式建议将对象构造代码从产品类中抽取出来， 并将其放在一个名为生成器(Builder)的独立对象中。该设计模式实现了构建和装配的解耦，适用于复杂对象的构造。

构成

1. 抽象生成器类（Builder）
2. 具体生成器类
3. 产品类

实例

生产自行车是一个复杂的过程，它包含了车架，车座等组件的生产。而车架又有碳纤维，铝合金等材质
的，车座有橡胶，真皮等材质。对于自行车的生产就可以使用建造者模式。

public class Demo {
    public static void main(String[] args) {
        BikeBuilder bb = new BikeBuilder();
        Bike bike = bb.createBike();
    }
}

class Bike{
    private String frame;
    private String seat;

    public String getFrame() {
        return frame;
    }

    public void setFrame(String Frame) {
        this.frame = frame;
    }

    public String getSeat() {
        return seat;
    }

    public void setSeat(String seat) {
        this.seat = seat;
    }
}
abstract class Builder{
    protected Bike mBike = new Bike();    //对子类可见
    public abstract void buildFrame();
    public abstract void buildSeat();
    public abstract Bike createBike();
}

class BikeBuilder extends Builder{

    @Override
    public void buildFrame() {
        mBike.setFrame("铝合金车架");
    }

    @Override
    public void buildSeat() {
        mBike.setFrame("真皮车座");
    }

    @Override
    public Bike createBike() {
        return mBike;
    }
}

如果参数很多，还可以使用链式的Builder，如下示例：

public class Demo2 {
    Phone phone = new Phone.Builder().cpu("AMD").screen("LG").mainboard("ASUS").memory("WD").build();
}
class Phone {
    private String cpu;
    private String screen;
    private String memory;
    private String mainboard;

    public Phone(Builder builder){
        cpu = builder.cpu;
        screen = builder.screen;
        memory = builder.memory;
        mainboard = builder.mainboard;
    }
    public static final class Builder{
        private String cpu;
        private String screen;
        private String memory;
        private String mainboard;
        public Builder(){};

        public Builder cpu(String cpu){
            this.cpu = cpu;
            return this;
        }
        public Builder screen(String screen){
            this.screen = screen;
            return this;
        }
        public Builder memory(String memory){
            this.memory = memory;
            return this;
        }
        public Builder mainboard(String mainboard){
            this.mainboard = mainboard;
            return this;
        }
        public Phone build(){
            return new Phone(this);
        }
    }
}