Casting or Variable type error in Java

Question

I have tried to do a simple math calculation for a formula involving variables. However, an error pops up in the compiler indicating that the variable types don't match. I have tried casting and changing the variable types, but they do not work. How do I fix this without destroying the basic format of my code.

I am not experienced at Java, so any pointers will help.

Here is the code. It is for a money conversion program. The error is in the second part of the code, the else part.

import java.util.Scanner;
public class MConvert
{
    public static void main (String[] args)
   {
     int penny, nickel, dime, quarter, halfDollar, dollar, fiveDollar, tenDollar,     twentyDollar, fiftyDollar, hundredDollar; 
     //can sub $ sign for dollar in variable, convention otherwise
     double totalMoney; 
     Scanner scan = new Scanner (System.in);
        System.out.println ("Are you converting to the total? If so, type true. \nIf you are converting from the total, then type false.");
       boolean TotalorNot = true;
        TotalorNot = scan.nextBoolean();


       if (TotalorNot) {

        System.out.println ("Type in the number of one-hundred dollar bills.");
        hundredDollar = scan.nextInt();
        System.out.println ("Type in the number of fifty dollar bills.");
        fiftyDollar = scan.nextInt();
        System.out.println ("Type in the number of twenty dollar bills.");
        twentyDollar = scan.nextInt();
        System.out.println ("Type in the number of ten dollar bills.");
        tenDollar = scan.nextInt();
        System.out.println ("Type in the number of five dollar bills.");
        fiveDollar = scan.nextInt();
        System.out.println ("Type in the number of one dollar bills or coins.");
        dollar = scan.nextInt();
        System.out.println ("Type in the number of half-dollar coins.");
        halfDollar = scan.nextInt();
        System.out.println ("Type in the number of quarter-dollar coins.");
        quarter = scan.nextInt();
        System.out.println ("Type in the number of dimes.");
        dime = scan.nextInt();
        System.out.println ("Type in the number of nickels.");
        nickel = scan.nextInt();
        System.out.println ("Type in the number of pennies coins.");
        penny = scan.nextInt();
        totalMoney = (hundredDollar * 100) + (fiftyDollar * 50) + (twentyDollar * 20) + (tenDollar * 10) + (fiveDollar * 5) + (dollar * 1) + ((double)halfDollar * 0.5) + ((double)quarter * 0.25) + ((double)dime * 0.1) + ((double)nickel * 0.05) + ((double)penny * 0.01); 
    System.out.println ("Here is total monetary value of the bills and coins you entered: " + totalMoney);




}    else {

        System.out.println ("Type in the total monetary value:");
        totalMoney = scan.nextDouble();
        hundredDollar = ((int)totalMoney / 100);
        fiftyDollar = ((int)totalMoney - (hundredDollar * 100)) / 50;
        twentyDollar = ((int)totalMoney - (fiftyDollar * 50)) / 20;
        tenDollar = ((int)totalMoney - (twentyDollar * 20)) / 10;
        fiveDollar = ((int)totalMoney - (tenDollar * 10)) / 5;
        dollar = ((int)totalMoney - (fiveDollar * 5)) / 1;
        (double) halfDollar = (totalMoney - (dollar * 1)) / 0.5;
        quarter = ((int)totalMoney - (halfDollar * 0.5)) / 0.25;
        dime = ((int)totalMoney - (quarter * 0.25)) / 0.1;
        nickel = ((int)totalMoney - (dime * 0.1)) / 0.05;
        penny = ((int)totalMoney - (nickel * 0.05)) / 0.01;

        System.out.println (hundredDollar + " hundred dollar bills");
        System.out.println (fiftyDollar + " fifty dollar bills");
        System.out.println (twentyDollar + " twenty dollar bills");
        System.out.println (tenDollar + " ten dollar bills");
        System.out.println (fiveDollar + " five dollar bills");
        System.out.println (dollar + " one dollar bills or coins");
        System.out.println (halfDollar + " half-dollar coins");
        System.out.println (quarter + " quarter-dollar coins");
        System.out.println (dime + " dimes");
        System.out.println (nickel + " nickel");
        System.out.println (penny + " penny");

    }


}

}

Answer 1

(double) halfDollar = (totalMoney - (dollar * 1)) / 0.5;

Is entirely wrong , first remove this instruction.

Also change your code with below lines.

quarter = (int)((totalMoney - (halfDollar * 0.5)) / 0.25);
dime = (int) ((totalMoney - (quarter * 0.25)) / 0.1);
nickel =(int)( (totalMoney - (dime * 0.1)) / 0.05);
penny = (int)((totalMoney - (nickel * 0.05)) / 0.01);

You also need to improve logic of your code, I can clearly see it do not serve what you want to achieve.

Answer 2

(double) halfDollar = (totalMoney - (dollar * 1)) / 0.5;

What are you trying to achieve with the double cast on the halfDollar. Remove that first. It took me 5 mins to find out why there were so many red lines in your code.

Next, you can do a simple case like this:-

halfDollar = (int)((totalMoney - (dollar * 1)) / 0.5);

But its not advisable to cast double values to int as you may tend to lose a lot of decimal data. Why not simple have all penny, nickel, dime, quarter, halfDollar, dollar, fiveDollar, tenDollar,twentyDollar, fiftyDollar, hundredDollar; as double itself?

Answer 3

The problem is in the following line:

(double) halfDollar = (totalMoney - (dollar * 1)) / 0.5;

What is the meaning of the (double) here? You cannot cast the left side of a variable assignment (the variable itself) to a double. The variable is declared to be an int, and that cannot be changed. Never.

This line compiles (but may be incorrect concerning semantics):

halfDollar = (int) ((totalMoney - (dollar * 1)) / 0.5);

Apart from that: I don't think, the program does, what you want it to do...

Answer 4

At this line ((int)totalMoney - (tenDollar * 10)) / 5;

the cast is applied to just totalMoney

to cast the value of whole expression you must do this

(int)(totalMoney - (tenDollar * 10)) / 5);