I am implementing Hierarchical Builder Pattern. I have used generics to make return type of my Parent Builder setter as that for child. Still I am facing problem when I use the child setter method after calling parent setter method. I don't want to define my child specific method (setEngine(String) here) in my Parent Builder. Is there any other way around for this problem?
I have made an example snippet for the mentioned problem, identical to this case.
CarFactory -> It returns the object of specific car that user wants
Car -> Parent for all Car types, Swift, Duster etc
Swift -> Specific car
Parent->Child Hierarchy
Car -> Swift
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();
}
}
In Drivers.java class I am not able to use setEngine() method after setSeat() method, this.factory().getSwiftDesire().setSeat(4).setEngine("CC").build(); I don't want to declare setEngine in parent class, is there any way around for same?
Thank you in advance!
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