Question

I’m trying to put a try-catch into a procedure type method but I’m 95% sure it has to be a function type. What I’m trying to accomplish is to make my code shorter in the main. One of the biggest things I thought of was to put a try-catch into a method and call the method.

The thing is, it will validate the input if it is a integer or not- it even catches the exceptions the problem is that it doesn’t “remember” the validated input once it continues on with the program/calculates. Here’s the part of the code I’m having trouble with.

 public static void tryCatchNum(double value)
 {
    while(true)
    {
    try
    {
        Scanner iConsole = new Scanner(System.in);
        value = Double.parseDouble(iConsole.nextLine());
            System.out.println(" ");
        break;
    }
    catch(NumberFormatException e)
    {
        System.out.println("NumberFormatException error has oocured. Please try again.");
    }
}

}

And here is the entire program:

    import java.util.Scanner;

    public class ch7exercise1
{
public static double compound(double oA, double cI)
{
    return roundCent((oA*(Math.pow((1+(percent(cI))),10))));
}

public static double percent(double interest)
{
    return interest/100.0;
}

public static double roundCent(double amount)
{
    return ((Math.round(amount*100))/100.0); //100.0 is mandatory.
}

public static void tryCatchNum(double value)
{
    while(true)
    {
        try
        {
            Scanner iConsole = new Scanner(System.in);
            value = Double.parseDouble(iConsole.nextLine());
            System.out.println(" ");
            break;
        }
        catch(NumberFormatException e)
        {
            System.out.println("NumberFormatException error has oocured. Please try again.");
        }
    }
}

@SuppressWarnings("unused")
public static void main(String[] args)
{
    boolean f = true;
    boolean f2 = true;
    double origAmount = 0;
    double compInterest = 0;
    double total = 0;

    Scanner iConsole = new Scanner(System.in);

    System.out.println("10 year Compound Interest Claculator\n");

    System.out.println("Input amount of money deposited in the bank");

    tryCatchNum(origAmount);

    System.out.println("Input compouded interest rate. (If the compound interest is 3% input 3)");

    tryCatchNum(compInterest);

    total = compound(origAmount,compInterest);

    System.out.println("$"+total);


}

}

Answer 1

Java arguments are passed by value. You’re passing 0 to the tryCatchNum method. A copy of the value is passed to the method. This method assigns a new value to its own copy, and then returns. So the original value is still 0.

You must not pass anything to the method. Instead, the method must return the value it has validated. Also, consider using a more appropriate method name:

public double readDoubleValue() {
    ...
    return value;
}

And in the main method:

double origAmount = readDoubleValue();