public class Car2Demo {
	public static void main(String[] args) {
		Car2 ford = new Car2("Ford", 20, 10, 500);
		System.out.println(ford);
		ford.drive(100);
		System.out.println("Is empty? " + ford.isEmpty());
		System.exit(0);
	}
}

class Car {
	private String name;
	private double gallons;
	private double mpg;	//miles per gallon

	public Car(String name, double gallons, double mpg) {	//constructor
		if (gallons < 0) {
			System.err.println("gallons " + gallons
				+ " can't be negative");
			System.exit(1);
		}

		if (mpg < 0) {
			System.err.println("mpg " + mpg + " can't be negative");
			System.exit(1);
		}

		this.name = name;
		this.gallons = gallons;
		this.mpg = mpg;
	}

	public String toString() {
		return name + " has " + gallons + " gallons, gets " + mpg
			+ " mpg, could go " + gallons * mpg + " more miles";
	}

	public boolean isEmpty() {
		return gallons <= 0;	//should never be negative
	}

	public void drive(double miles) {	//how many miles we want to go

		//How many miles will we go?
		double will = Math.min(miles, gallons * mpg);

		gallons -= will / mpg;
	}

	//Siphon gas from the other Car into this one.
	//g is the number of gallons we want to siphon.

	public void siphon(Car other, double g) {

		//How many gallons will we siphon?
		double will = Math.min(g, other.gallons);

		gallons += will;
		other.gallons -= will;
	}
}

class Car2 extends Car {
	private double _price;	//can't have field and method with same name

	public Car2(String name, double gallons, double mpg, double _price) {
		super(name, gallons, mpg);
		this._price = _price;
	}

	public String toString() {
		return super.toString() + ", price == " + _price;
	}

	public double price() {
		return _price;
	}
}