public/subjects/java/piscine/Builder

Builder

Instructions

Now let's implement the Builder Design Pattern

classDiagram
class Housing {
    <<interface>>
    +setSize(int size)*
    +setPrice(int price)*
    +setRooms(int rooms)*
    +setName(String name)*
}
class House {
    +setSize(int size)
    +setPrice(int price)
    +setRooms(int rooms)
    +setName(String name)
    +toString() String
}
class Apartment {
    +setSize(int size)
    +setPrice(int price)
    +setRooms(int rooms)
    +setName(String name)
    +toString() String
}
class HousingBuilder {
    <<interface>>
    +setSize(int size)* HousingBuilder
    +setPrice(int price)* HousingBuilder
    +setRooms(int rooms)* HousingBuilder
    +setName(String name)* HousingBuilder
    +build()* Housing
}

class HouseBuilder {
    -House house
    +setSize(int size) HousingBuilder
    +setPrice(int price) HousingBuilder
    +setRooms(int rooms) HousingBuilder
    +setName(String name) HousingBuilder
    +build() Housing
}
class ApartmentBuilder {
    -Apartment apartment
    +setSize(int size) HousingBuilder
    +setPrice(int price) HousingBuilder
    +setRooms(int rooms) HousingBuilder
    +setName(String name) HousingBuilder
    +build() Housing
}

Housing <|.. Apartment
Housing <|.. House
HousingBuilder <|.. ApartmentBuilder
HousingBuilder <|.. HouseBuilder

Here is the matching class diagram. Create the matching classes in the matching files.

The Apartment and House class should have an empty constructor.

The toString method of Apartment should return : Apartment{size=<size>, price=<price>, rooms=<rooms>, name='<name>'}
The toString method of House should return : House{size=<size>, price=<price>, rooms=<rooms>, name='<name>'}

Usage

Here is a possible ExerciseRunner.java to test your function :

public class ExerciseRunner {

    public static void main(String[] args) {
        Housing house = new HouseBuilder()
                .setName("Maison")
                .setRooms(4)
                .setSize(80)
                .setPrice(100000)
                .build();
        Housing apartment = new ApartmentBuilder()
                .setName("Appart")
                .setRooms(2)
                .setSize(30)
                .setPrice(25000)
                .build();

        System.out.println(house);
        System.out.println(apartment);
    }
}

and its output :

$ javac *.java -d build
$ java -cp build ExerciseRunner 
House{size=80, price=100000, rooms=4, name='Maison'}
Apartment{size=30, price=25000, rooms=2, name='Appart'}
$

Notions

Class diagram