Try catch loop problems :'(

I'm trying to get this code segment to repeat while the exception is caught. I don't see any errors in the code, neither does the compiler, except for the local boolean declared to set the "i" to true, it says it is never read. The program terminates before it is able to execute the account method.

Code:

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//Import
import java.util.Scanner;
import java.util.InputMismatchException;
//End import
// ----------------------------------------------------------------------
//Begin WelcomeScreen Class
public class WelcomeScreen
{
        Scanner input = new Scanner(System.in); //Create scanner object
        DataStorage data = new DataStorage(); //Create DataStorage object for use
       
//Begin welcome       
       
        public void welcome()//Declare method
        {
               
                System.out.print("Welcome. Please enter your name\n\n"); //Display welcome message
                String userName = input.next(); //Wait for input
                data.setname(userName); //Value is set through setname's parameters
                /*
                * Removed for redundancy. See method "account"
                * System.out.print("\nHello " + userName); //Display text + input
                */
               
        }//End welcome
       
//Begin account        method
       
        public void account()//Declare method
               
        {
                boolean i = true;//Local variable declare for loop segment
               
        try//Try segment containing loop
        {
               
               
               
                while (i = false)
               
                {
                                System.out.printf("\n\n%s please enter your account number", data.getname());
                                int account = input.nextInt();//Input = int
                                data.setaccount(account);//Store input in DatStorage class
                               
                }//End while loop
               
                       
        } catch (InputMismatchException e)//Catch exception when input ! int
       
        {
               
        /*
        * System.out.print(e);//Print exception for error checking
        */
               
        i = false;//Variable checked by while statement to repeat loop after exception catch
       
        }//End Catch
       
        }//End account method
       
       
       
       
       
       
       
       
}//End WelcomeScreen Class

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Code:

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while (i = false)

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...should be:

Code:

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while (i == false)

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EDIT:
Actually there's more to it than that... The while loop should be AROUND the try-catch statement, and i should be set to **true** when you want the loop to stop.

Basically this is the idea:

Code:

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set your variable to false
while (your variable is false) {
    try {
        something
        break loop by setting variable to true
    } catch (exception) {
        tell user
    }
}

---

Alright, I followed your instructions, however I still could not repeat the while statement if the user threw an exception. Here is the code:

Code:

---

public void account()//Declare method
               
        {//Begin method
                boolean i = false;
               
                while (i = false);
                {//Begin while
                        try
                        {//Begin try
                               
                                System.out.printf("\n\n%s please enter your account number: ", data.getname());
                               
                                int account = input.nextInt();//Input = int
                               
                                data.setaccount(account);//Store input in DatStorage class
                               
                                i = true;                       
                               
                        } catch (InputMismatchException e) //End Try
                       
                        {//Begin catch
                               
                                System.out.println(e + "\n\nTry again.");
                                i = false;
                        }//End catch
                       
                       
                       
                       
                }//End while
        }//End method

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It terminates after printing out the exception plus the text. i = false; is never evaluated by the while to repeat the loop.

Code:

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                while (i = false);
                {//Begin while

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This does not begin a while statement. Basically, these two lines translate to this:

Code:

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while (i = false) { }
//Begin while

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Therefore you should be doing this instead:

Code:

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while (i == false)
{ //Begin while

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Additionally, notice the double equals sign in my code above. = is used to assign a value to a variable (such as when you declare i on line 4), whereas == is used to compare two values. (More info here.)

Thank you for the link.

Now, the code DOES work, however, it spirals into an infinite loop once the exception is thrown. I tried modifying the code to break once the exception is thrown, but that just terminates the program all together. I tried i = false; and then break, hoping the while statement would reread the value and compare, it didn't. How do I prevent the the infinite loop after the exception gets caught?

Code:

---

public void account()//Declare method
               
        {//Begin method
                boolean i = false;
               
                while (i == false)
                {//Begin while
                        try
                        {//Begin try
                               
                                System.out.printf("\n\n%s please enter your account number: ", data.getname());
                               
                                int account = input.nextInt();//Input = int
                               
                                data.setaccount(account);//Store input in DatStorage class
                               
                                i = true;
                               
                        } catch (InputMismatchException e) //End Try
                       
                        {//Begin catch
                               
                                System.out.println(e + "\n\nTry again.");
                               
                        }//End catch
                       
                       
                       
                       
                }//End while
        }//End method

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Quote:

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Originally Posted by Romally

Thank you for the link.

Now, the code DOES work, however, it spirals into an infinite loop once the exception is thrown. I tried modifying the code to break once the exception is thrown, but that just terminates the program all together. I tried i = false; and then break, hoping the while statement would reread the value and compare, it didn't. How do I prevent the the infinite loop after the exception gets caught?

Code:

---

public void account()//Declare method
               
        {//Begin method
                boolean i = false;
               
                while (i == false)
                {//Begin while
                        try
                        {//Begin try
                               
                                System.out.printf("\n\n%s please enter your account number: ", data.getname());
                               
                                int account = input.nextInt();//Input = int
                               
                                data.setaccount(account);//Store input in DatStorage class
                               
                                i = true;
                               
                        } catch (InputMismatchException e) //End Try
                       
                        {//Begin catch
                               
                                System.out.println(e + "\n\nTry again.");
                               
                        }//End catch
                       
                       
                       
                       
                }//End while
        }//End method

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When the nextInt() method throws an Exception (because it can't read an int) it doesn't read anything at all; when you attempt to read an int using that same method, the same will be checked and the same Exception will be thrown again. A solution would be, when an Exception is thrown, to read and get rid of the entire offending line using the nextLine() method.

kind regards,

Jos

MWUAHAHAHA I GOT IT!!! WOOOOT!

I had to change all the methods to string and parse int to be stored if true. It was the only way it would let me use nextLine();

Code:

---

public void account()//Declare method
               
        {//Begin method
                boolean i = false;
               
                while (i == false)
                {//Begin while
                        try
                        {//Begin try
                               
                                System.out.printf("\n\n%s please enter your account number: ", data.getname());
                               
                                String account = input.nextLine();//Input = int
                                Integer.parseInt(account);
                               
                                data.setaccount(account);//Store input in DatStorage class
                               
                                i = true;
                               
                        } catch (NumberFormatException e) //End Try
                       
                        {//Begin catch
                               
                                System.out.println(e + "\n\nTry again.\n\n");
       
                        }//End catch

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Mwuahahaha thats so awesome. I've been thinking about this and trying anything I could think of for TWO days! Man this feels awesome. Thanks for the help!

Quote:

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Originally Posted by Romally

MWUAHAHAHA I GOT IT!!! WOOOOT!

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Nurse, syringe please ...

kind regards,

Jos ;-)