Question

Write a CarInterface to have the following method headers:

public int pumpGas(int gas); // no more than 15 gallons return cost at $3.25 per gallon

public void goFast(int fast); // add fast to speed

public void goSlow(int slow); subtract slow from speed but if negative set speed to zero

public void stop(); //set speed to zero

Make sure to write a toString for the class Car.

Test the Car class in main by creating an array of size 10. Test all the methods in interface.

Answer 1

//CarInterface.java
public interface CarInterface {
    public int pumpGas(int gas); // no more than 15 gallons return cost at $3.25 per gallon

    public void goFast(int fast); // add fast to speed

    public void goSlow(int slow); //subtract slow from speed but if negative set speed to zero

    public void stop(); //set speed to zero
}

/////////////////////////////////////////////////////////////////////////////////

//Car.java
public class Car implements CarInterface{
  private int gas;
  private int speed;

  @Override
  public int pumpGas(int gas) {
    this.gas = gas;
    if(gas <= 15){
      return (int) (gas*3.25);
    }
    else{
      return -1;
    }
  }

  @Override
  public void goFast(int fast) {
    speed += fast;
  }

  @Override
  public void goSlow(int slow) {
    speed -= slow;
    if(speed<0){
      speed = 0;
    }
  }

  @Override
  public void stop() {
    speed = 0;
  }

  public String toString() {
    return "Car{" +
            "gas=" + gas +
            ", speed=" + speed +
            '}';
  }
}

/////////////////////////////////////////////////////////////////////////////////

//TestCar.java
public class TestCar {
    public static void main(String[] args) {
        CarInterface cars[] = new Car[10];

        for(int i = 0;i<cars.length;i++){
            cars[i] = new Car();
        }

        for(int i = 0;i<cars.length;i++){
            System.out.println(cars[i].pumpGas(i));
        }
        System.out.println();

        cars[0].goFast(34);
        cars[3].goFast(67);
        cars[4].goFast(23);
        cars[5].goFast(1);
        cars[8].goFast(7);

        for(int i = 0;i<cars.length;i++){
            System.out.println(cars[i]);
        }
        System.out.println();

        cars[0].goSlow(3);
        cars[3].goSlow(4);
        cars[4].goSlow(6);
        cars[5].stop();
        cars[8].goSlow(1);

        for(int i = 0;i<cars.length;i++){
            System.out.println(cars[i]);
        }
        System.out.println();

    }
}

/////////////////////////////////////////////////////////////////////////////////