Question

Needs Help In Java Programming language

Exceptional Cars

Purpose To review interfaces and exception usage.

Directions

Your task is to write a class called Car. Your class should have the following fields and methods:

private int position
private boolean headlightsOn

public Car() - a constructor which initializes position to 0 and headlightsOn to false

public Car(int position) - a constructor which initializes position to the passed in value and headlightsOn to false, and it should throw a NegativeNumberException with a custom message when a negative number is passed
public String toString() - a method that returns a String of form
"This car is in position *position* and has its headlights on if headlightsOn is True” "This car is in position *position* and has its headlights off if headlightsOn is False”

Note : *position* denotes the value of the variable position

Your Car class also needs to implement a drivable interface which you will also make that includes the methods:
public boolean toggleHeadlights() - which toggles the headlightsOn variable between true and false

public int forward(int amount) - which adds the amount passed in to the position of the car, and throws a NegativeNumberException with a custom message when a negative number is passed

You will create the NegativeNumberException class which will have the following methods:
public NegativeNumberException() - a constructor that creates an exception with a blank message

public NegativeNumberException(String message) - a constructor which passes a message to the NegativeNumberException’s parent exception class

So in summary you are making a Car class, a drivable interface, and a custom exception

Testing:

You also need to create a class called Driver.java with a main method.

In main:
Create two Car objects

Surround all of the forward method calls with a single try catch block

Call forward on both of the Cars
Make one of the Cars throw a NegativeNumberException

Print out the toString of both cars

Example Output:

NegativeNumberException: You can't go forward a negative amount

at Car.forward(Car.java:15)
at Driver.main(Driver.java:13)

This car is in position 21 and has its headlights off

This car is in position 31 and has its headlights on

Answer 1

import java.io.*;
import java.util.*;

//Exception class that denotes negative number
class NegativeNumberException extends Exception{
    NegativeNumberException(){

    }

    NegativeNumberException(String msg){
        super(msg);
    }
}

//Car class
class Car{
    //Private member variables
    private int position;
    private boolean headLightsOn;

    //Default constructor
    public Car(){
        position = 0;
        headLightsOn = false;
    }

    //Argumented constructor
    public Car(int position){
        this.position = position;
        headLightsOn = false;
    }

    @Override
    public String toString(){
        return "This car is in position "+position+" and its headlights "+(headLightsOn?"On":"Off");
    }

    //Method to toggle head lights
    public boolean toggleHeadLights(){
        headLightsOn =  !headLightsOn;
        return headLightsOn;
    }

    //method that takes car forward
    public int forward(int amount) throws NegativeNumberException {
        if(amount<0){
            throw new NegativeNumberException("You can't go forward a negative amount");
        }
        this.position += amount;
        return this.position;
    }
}

class Driver{
    public static void main(String[] args) {
        Car c1 = new Car();
        Car c2 = new Car(5);

        try {
            c1.forward(5);
            c2.forward(-2);
        } catch (NegativeNumberException e) {
            System.out.println(e);
        }
    }
}

OUTPUT :