How to make all Builder methods required?

Question

I am building a class car with an engine, gearbox, clutch, etc. I don't want a bloated constructor that takes 7 parameters, so I decided to use the builder pattern. All parts are required. However, how can I get a user of the Car class to use all the configuration tools for the parts since they are all required? Throw exceptions?

public class Car {

    private Engine engine;
    private Chassis chassis;
    private GearBox gearBox;
    private Coupe coupe;
    private Exterior exterior;
    private Interior interior;
    private Clutch clutch;

    public Car(Builder builder) {
        engine = builder.engine;
        chassis = builder.chassis;
        gearBox = builder.gearBox;
        coupe = builder.coupe;
        exterior = builder.exterior;
        interior = builder.interior;
        clutch = builder.clutch;
    }

    public static class Builder {

        private Engine engine;
        private Chassis chassis;
        private GearBox gearBox;
        private Coupe coupe;
        private Exterior exterior;
        private Interior interior;
        private Clutch clutch;


        private Car build() {
            return new Car(this);
        }

        public Builder setEngine(@NonNull Engine engine) {
            this.engine = engine;
            return this;
        }

        public Builder setChassis(@NonNull Chassis chassis) {
            this.chassis = chassis;
            return this;
        }

        public Builder setGearBox(@NonNull GearBox gearBox) {
            this.gearBox = gearBox;
            return this;
        }

        public Builder setCoupe(@NonNull Coupe coupe) {
            this.coupe = coupe;
            return this;
        }

        public Builder setExterior(@NonNull Exterior exterior) {
            this.exterior = exterior;
            return this;
        }

        public Builder setInterior(@NonNull Interior interior) {
            this.interior = interior;
            return this;
        }

        public Builder setClutch(@NonNull Clutch clutchs) {
            this.clutch = clutchs;
            return this;
        }

    }


}

I want the user to call ALL linker settings, and not an additional subset of them. How to do it?

Is there any other way to build a car without a huge constructor that takes so many parameters?

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Answer 1

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Answer 2

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class Engine {}
class Door {}
class Car {
    Car(Engine engine, Door door) {

    }
}

class CarBuilder {
    private Engine engine;

    public CarWithEngineBuilder withEngine(Engine engine) {
        this.engine = engine;
        return new CarWithEngineBuilder();
    }

    class CarWithEngineBuilder {
        private Door door;


        public CarWithEngineAndDoor withDoor(Door door) {
            this.door = door;
            return new CarWithEngineAndDoor();
        }

        class CarWithEngineAndDoor {
            public Car build() {
                return new Car(engine, door);
            }
        }
    }
}

class TestStuff {
    {
        Car c = new CarBuilder().withEngine(new Engine()).withDoor(new Door()).build();
    }
}

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Answer 3

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The director must call all the methods necessary for the interface constructor (in your case, "assembly mechanism, assembly of the compartment, etc."). A class that implements the Builder interface must override all methods or the code does not even compile.