classes, Car class, Exercise 02 slide 47

package class170706;

public class Car {
    // min number of digits in a valid car number
    private final int MIN_DIGITS_NO = 7;
    // max number of digits in a valid car number
    private final int MAX_DIGITS_NO = 8;

    // properties
    private int carNumber; // number of digits in the valid range
    private int speed; // positive for forward, negative for reverse

    // return car number
    public int getCarNumber() {
        return this.carNumber;
    }

    // set car Number
    public boolean setCarNumber(int carNumber) {
        // if argument is invalid
        if (!isValidNumber(carNumber)) {
            // do nothing and return false
            return false;
        }
        this.carNumber = carNumber;
        return true;
    }

    // check if carNumber is valid
    // return true if valid, false otherwise
    private boolean isValidNumber(int carNumber) {
        // valid number as defined by MIN_DIGITS_NO and MAX_DIGITS_NO
        int digitCount= (int)(Math.log10(carNumber)+1);
        return (digitCount >= MIN_DIGITS_NO & digitCount <= MAX_DIGITS_NO);
    }

    // return speed
    public int getSpeed() {
        return this.speed;
    }

    // accelerate: increase speed by 1, at the current direction
    public void accelerate() {
        this.speed += this.speed >= 0 ? 1 : -1;
    }

    // decelerate: decrease speed by 1
    // negative number indicate driving in reverse
    public void decelerate() {
        this.speed -= this.speed >= 0 ? 1 : -1;
    }

    // stop the car
    public void stop() {
        this.speed = 0;
    }

    @Override
    public String toString() {
        return String.format("[carNumber=%d, speed=%d]", this.carNumber,
                this.speed);
    }

}