Drive/Park/Fill Up

/**An application that loops and asks the user if they want to:
 * 	Drive, Fill up gas or Park.  at the end of the trip the total
 * 	distance is displayed along with remaining gas.
 *
 * Created by Justin Gauthier
 * On "November 19, 2014"
 * To Perform Drive, Park, or Fillup
 */

package driveparkfillup;
import java.util.*;

public class Main
{
    public static void main(String[] args)
    {
        //Creates a Scanner called scan
        Scanner scan = new Scanner(System.in);

        //Asks for number of litres that can be held
        System.out.println("Please enter how many litres your tank holds.");
        int tankSize = scan.nextInt();

        //Asks for number of litres in tank
        System.out.println("Please enter the number of litres you have.");
        int initialAmount = scan.nextInt();

        if(initialAmount > tankSize)	//check if too much gas
        {
        	System.out.println("Cant have more gas in tank than tank size!");
        	System.exit(0);
        }

        if(initialAmount < 0)			//check if invalid gas
        {
        	System.out.println("Cant have less than zero gas!");
        	System.exit(0);
        }

        boolean stillDriving = true;		//Determines if you are still driving
        double youHave = initialAmount; 	//Litres left in tank
        double km = 0; 						//KM travled Total
        double totalLitres = initialAmount; 			//The number of liters in the end

        while(stillDriving)
        {
        	//Asks what the user would like to do
            System.out.print("Would you like to Drive(1), Fill Tank(2), or Park(3)? ");
            int choice = scan.nextInt();

            switch(choice)
            {
            case(1):
            	//Ask user how far to drive
            	System.out.print("Enter the number of KM you drive: ");
            	double distance = scan.nextDouble();
            	km += distance;					//increase total distance
            	double youUsed = distance / 10;	//update gas used
            	totalLitres -= youUsed;			//update total litres
            	youHave -= youUsed;				//update what is left in the tank
            	if (youHave >= 0)				//check if you didn't run out of gas
                {
                    System.out.println("You used " + youUsed + " Litres, and have " + youHave + " Litres left.");
                } else { //repeats start of loop and updates values to beofore error
                    System.out.println("Error! Not enough gas!");
                        km -= distance;                         //subtracts distance input, to before error value
                        totalLitres += youUsed;                 //adds what was used, to before error value
                        youHave = totalLitres;                 //adds waht was input, to before error value
                    break;
                }
            	break;

            case(2):
            	//Ask user how many litres to add to the tank
            	System.out.print("How many litres did you add? ");
            	double newLitres = scan.nextDouble();
            	youHave += newLitres;
                totalLitres += newLitres;
            	if ((youHave <= tankSize))
            	{
            		System.out.println("You have " + youHave + " Litres in your tank.");
            	} else { //repeats start of loop and updates values to beofore error
            		System.out.println("Error! Too much gas!");
                            youHave -= newLitres;               //subtracts what was input, to before error value
                            totalLitres = youHave;              //updates total litres, to before error value
            	}
            	break;

            case(3):
            	//User chose to park
            	System.out.println("You have " + totalLitres + " Litres in your tank and have driven " + km + " KM");
            	stillDriving = false;
            	break;

            default:
            	//User entered invalid value
            	System.out.println("You have entered an invalid choice!");
            	break;
            }
        }
        scan.close();
    }
}