Question

我正在实现Hierarchical Builder Pattern。我已经使用泛型来将我的Parent Builder setter的返回类型设为孩子的返回类型。在调用父级setter方法后使用子级setter方法时，仍然遇到问题。我不想在我的父代构建器中定义我的孩子特定的方法（此处为setEngine（String））。还有其他解决方法吗？

我针对上述问题制作了一个示例片段，与本例相同。

CarFactory-> 返回用户想要的特定汽车的对象

汽车-> 为所有汽车类型（Swift，Duster等）的父级

Swift-> 特定汽车

父级->儿童层次结构

汽车->斯威夫特

CarBuilder-> SwiftBuilder

Car.java

 package Builders;

 public class Car {
   int tyre;
   int seat;
   public int getTyre() {
       return tyre;
   }
   public void setTyre(int tyre) {
       this.tyre = tyre;
   }
   public int getSeat() {
       return seat;
   }
   public void setSeat(int seat) {
       this.seat = seat;
       
   }
   
}

Swift.java

package Builders;

public class Swift extends Car {
    boolean safetyAirbag;
    String engine;
    
    public boolean isSafetyAirbag() {
        return safetyAirbag;
    }

    public String getEngine() {
        return engine;
    }

    public void setSafetyAirbag(boolean safetyAirbag) {
        this.safetyAirbag = safetyAirbag;
    }

    public void setEngine(String engine) {
        this.engine = engine;
    }


}

CarBuilder.java

package Builders;

public abstract class CarBuilder {
        int tyre;
        int seat;
         
        public abstract <B extends CarBuilder>B self();
        public abstract <T extends Car>T typeOfCar();
            
        public <B extends CarBuilder>B setTyre(int tyre) {
            this.tyre = tyre;
            return self();
        }
        
        public  <B extends CarBuilder> B setSeat(int seat) {
            this.seat = seat;
            return self();
        }
        public <C extends Car>C build()
        {   C car=this.typeOfCar();
            car.setSeat(seat);
            car.setTyre(tyre);
            return car;
        }
    
        
}

SwiftBuilder.java

package Builders;

public class SwiftBuilder extends CarBuilder {
    String engine;
    @Override
    public
    SwiftBuilder self() {
        
        return this;
    }

    @Override
    public
    Swift typeOfCar() {
        
        return new Swift();
    }

    public SwiftBuilder setEngine(String string) {
        this.engine=string;
        return this;
    }
    public Swift build()
    {   Swift s=(Swift)super.build();
        return s;
    }

}

CarFactory.java

package Builders;

public class CarFactory {
    public SwiftBuilder getSwiftDesire()
    {
        return new SwiftBuilder();
    }
}

Drivers.java

package Builders;

public class Drivers {
    Swift getMyCar() {
        Swift s= this.factory().getSwiftDesire().setSeat(4).setEngine("CC").build();
        return s;
    }
    CarFactory factory() {
        return new CarFactory();
    }
}

在Drivers.java类中，我无法在setSeat（）方法之后使用setEngine（）方法， this.factory（）。getSwiftDesire（）。setSeat（4）.setEngine（“ CC”）。build（）; 我不想在父类中声明setEngine，是否有相同的方法？

提前谢谢！

Answer 1

您需要在CarBuilder中的类级别而不是方法级别使用泛型：

package Builders;

public abstract class CarBuilder<B extends CarBuilder<B, C>, C extends Car> {
    int tyre;
    int seat;

    public abstract B self();

    public abstract C typeOfCar();

    public B setTyre(int tyre) {
        this.tyre = tyre;
        return self();
    }

    public B setSeat(int seat) {
        this.seat = seat;
        return self();
    }

    public C build() {
        C car = this.typeOfCar();
        car.setSeat(seat);
        car.setTyre(tyre);
        return car;
    }

}

然后定义您的SwiftBuilder：

package Builders;

public class SwiftBuilder extends CarBuilder<SwiftBuilder, Swift> {
    String engine;

    @Override
    public SwiftBuilder self() {

        return this;
    }

    @Override
    public Swift typeOfCar() {

        return new Swift();
    }

    public SwiftBuilder setEngine(String string) {
        this.engine = string;
        return this;
    }

    public Swift build() {
        Swift s = super.build();
        return s;
    }

}

它有效。

分层构建器模式的实现

1 个答案: