Why don't loops work properly inside methods? (JAVA)

Here is the code I am working with.

The first problem I am having is that when I run it, the loop in the method "che_amo" doesn't work properly. It is supposed to keep asking for a cheque number and the cheque amount, until the user enters a -1 for a cheque number, then it is supposed to move on. But what happens is once the user enters in a -1 for a cheque number, it asks them again for a cheque number, and they must enter another -1 in order for it to move on.

If I take out "sub_total = che_amo();" in the method "gst", then the problem is solved. What is the reason for this?


My second problem is very similar to the first, except that the line "gst_amo = sub_total * gst;" in the method "gst" is returning the value of sub_total * gst, but it isn't taking the actual sub total, it is just taking the value that I declared the subtotal to be in the method "che_amo".

Could someone please help me figure this out? I would be greatly appreciative.

Thank you,
Nick Young.


public class SimpleMethods
{
/**
* replace this comment with your own
*
*/
public static void main()
{

balance();
header();
che_amo();
gst();


}


//End of Main
//////////////////////////////////////////////////////////
//Start of Methods

public static double balance()
{
double balance; //The starting balance of users account.
final double ovr_dft = 50.00; //Overdraft on users account. In this program, it is always 50 dollars!

balance = IO.readDouble("Please Enter Your Current Account Balance: ");
System.out.println("Your Current Account Balance is: " + balance);
System.out.println("You have an overdraft protection of " + ovr_dft);
System.out.println();

return balance;
}


public static void header()
{
System.out.print("Cheque No.");
System.out.print(" ");
System.out.print("Amount");
System.out.println();
}


public static double che_amo()
{
double cheque,
amount,
sub_total = 0.0;

cheque = IO.readDouble("Please Enter Cheque Number: ");
while (cheque > 0)
{
System.out.print(" " + cheque);
amount = IO.readDouble("Please Enter Cheque Amount: ");
System.out.print(" " + amount);

sub_total = sub_total + cheque;
cheque = IO.readDouble("Please Enter Cheque Number: ");
System.out.println();
}

return sub_total;
}


public static void gst()
{
double sub_total,
gst = 0.07,
gst_amo,
total;

sub_total = che_amo();
gst_amo = sub_total * gst;
System.out.println("The total GST is: " + gst_amo);
total = sub_total + gst;
System.out.println("You Owe a Total of: " + total);
}

}

for your first problem I would probably have to suggest that you use a do-while statement instead of a while statement. That should cut that -1 x 2 problem down.

for your second problem, I would suggest that you make a global value for subtotal instead of instances of the same value in different methods. Though I don't see why that wouldn't work as you have it, I haven't stared at it enough yet perhaps...


Jason

edit:
shouldn't the line

sub_total = sub_total + cheque;

actually be

sub_total = sub_total + amount;

to give you an actual total? why would you add check numbers?

are you sure the subtotal at the end of che_amo() is the number you want? did you check with a print statement to make sure?

Jason

for the first problem, you give your own solution. After calling the method che_amo() from the main(), you call it again from the gst() method. So the user has to end the loop twice. changing the while loop to a do..while loop doesnt help this. A do..while loop executes always once, a while loop doesn't have to execute at all, make sure you get the desired functionality in sight before you choose a program structure inhere.

Overall i have to mention the following: why don't you use the return value from your functions. You probably just need the returnvalue from your che_amo() function in the gst() function. So remove the call to che_amo() from the main() method and you should be fine. Don't you have to use the return from the balance method anywhere?

Seems to me this (probably homework assignment) still needs a lot of work.