Exception in Thread "main"

import java.util.Scanner;
import javax.swing.JOptionPane;

public class SalesCommission
{
    public static void main( String [] args )
		{
		double commissionRate;
		double item1Commission;
		double item2Commission;
		double item3Commission;
		double item4Commission;
		double totalCommission;
		int item1Quantity;
		int item2Quantity;
		int item3Quantity;
		int item4Quantity;
		int itemSelected;

		commissionRate = 0.09;
		item1Commission = 239.99 * commissionRate;
		item2Commission = 129.75 * commissionRate;
		item3Commission = 99.95 * commissionRate;
		item4Commission = 350.89 * commissionRate;
		item1Quantity = 0;
		item2Quantity = 0;
		item3Quantity = 0;
		item4Quantity = 0;
		itemSelected = 0;
		totalCommission = 200 + (item1Quantity * item1Commission) + (item2Quantity * item2Commission) + (item3Quantity * item3Commission) + (item4Quantity * item4Commission);

		Scanner input = new Scanner( System.in );
			System.out.println( "Enter item number. Enter -1 to quit." );
			itemSelected = input.nextInt();

		while( itemSelected != -1 )
		{
			if( itemSelected == 1 )
				{
				System.out.printf( "How many of item 1 did you sell?\n" );
				item1Quantity = item1Quantity + input.nextInt();
				}
			else if( itemSelected == 2 )
				{
				System.out.printf( "How many of item 2 did you sell?\n" );
				item2Quantity = item2Quantity + input.nextInt();
				}
			else if( itemSelected == 3 )
				{
				System.out.printf( "How many of item 3 did you sell?\n" );
				item3Quantity = item3Quantity + input.nextInt();
				}
			else if( itemSelected == 4 )
				{
				System.out.printf( "How many of item 4 did you sell?\n" );
				item4Quantity = item4Quantity + input.nextInt();
				}
			else
				{
				System.out.println( "Item number does not exist." );
				}
			System.out.println( "Enter item number. Enter -1 to quit." );
			itemSelected = input.nextInt();
		}

		String message = String.format( "Your commission is $%.2d", totalCommission );
		JOptionPane.showMessageDialog( null, message );


	}
}