public class DollarFormat
{
    /**
     Displays amount in dollars and cents notation. 
     Rounds after two decimal places. 
     Does not advance to the next line after output.
    */
    public static void write(double amount)
    {
        if (amount >= 0)
        {
            System.out.print('$');
            writePositive(amount);
        }
        else
        {
            double positiveAmount = -amount;
            System.out.print('$');
            System.out.print('-');
            writePositive(positiveAmount);
        }
    }
    
    //Precondition: amount >= 0;
    //Displays amount in dollars and cents notation. Rounds
    //after two decimal places. Omits the dollar sign.
    private static void writePositive(double amount)
    {
        int allCents = (int)(Math.round(amount * 100));
        int dollars = allCents / 100;
        int cents = allCents % 100; 
        System.out.print(dollars);
        System.out.print('.');

        if (cents < 10)
            System.out.print('0');
		System.out.print(cents);
    }

    /**
     Displays amount in dollars and cents notation. 
     Rounds after two decimal points. 
     Advances to the next line after output.
    */
    public static void writeln(double amount)
    {
        write(amount);
        System.out.println( );
    } 
}