CODEWITHSUNDEEP
java
Tom
Tom

Reputation: 1

How to debug a program that runs but doesn't stop?

I have written a program to sort numbers in both Ascending and Descending order. Here is the output:

"Enter numbers to sort" input numbers {4 3 2 6}

"Type 'A' for Ascending order 'B' for descending order" input A output: 2 3 4 6

This program runs giving the correct output except that it doesn't exit automatically in command prompt. When I press ctrl-c I get a message "exception in thread "main"".

I am trying to find where I went wrong for a while now but with no success.

Code:

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        System.out.println("Enter numbers to sort");
        String str = in.nextLine();
        String[] splitted = str.trim().split("\\s+");
        int len = splitted.length;
        int a[] = new int[len];
        for (int i = 0; i < len; i++) {
            a[i] = Integer.parseInt(splitted[i]);
        }
        boolean TryAgain = true;
        System.out.println("How to sort: Type 'A' for Ascending and 'B' for Descending order");

        while (TryAgain=true) {

            char SortType = in.next().charAt(0);

            if (SortType == 'A' || SortType == 'a' || SortType == 'B' || SortType == 'b') {// first if

                if (SortType == 'A' || SortType == 'a') {// second if loop
                    // code for sorting in Ascending order
                    for (int j = 0; j < len - 1; j++) {
                        for (int k = 0; k < len - j - 1; k++) {
                            if (a[k] > a[k + 1]) {
                                int n = a[k];
                                a[k] = a[k + 1];
                                a[k + 1] = n;
                            } // for
                        } // for
                    } // if
                    System.out.println("Numbers sorted in Ascending order:");
                    for (int m = 0; m < len; m++) {
                        System.out.print(a[m] + " ");
                    } // for
                    TryAgain = false;
                } // second if loop


                else {// second else
                        // code for sorting in Dscending order
                    for (int j = 0; j < len - 1; j++) {
                        for (int k = 0; k < len - j - 1; k++) {
                            if (a[k] < a[k + 1]) {
                                int n = a[k];
                                a[k] = a[k + 1];
                                a[k + 1] = n;
                            } // for
                        } // for
                    } // if
                    System.out.println("Numbers sorted in Dscending order:");
                    for (int m = 0; m < len; m++) {
                        System.out.print(a[m] + " ");
                    } // for
                    TryAgain = false;
                } // second else loop
            } // first if loop

            else {// first else
                TryAgain = true;
                System.out.println("Invalid input");
                System.out.println("Type 'A' for Ascending and 'B' for Descending order:");
            } // first else loop

        } // while loop


    }// main
}// class

Upvotes: 0

Views: 107

Answers (4)

Sanket Gupte
Sanket Gupte

Reputation: 357

When you type

   while(tryAgain=true)

It assigns true to tryAgain irrespective of what was assigned previously. This means that the loop will remain true no matter what. In your code we see that you have already initialized the boolean variable tryAgain to true. So, there is no need to do so again. This is the mistake you are making in the while loop thereby keeping I continuously active. Further in your code when you make the value of tryAgain false, it reinitialises itself in the while loop and keeps the loop going on. Instead when you write

    while(tryAgain)

It gives you the flexibility to change the value of tryAgain. So when you change its value to false, it remains false. Also if you are if you want, you could change your code to

    while(tryAgain==true)

Just to save the trouble of deleting ;). The above snippet will work in the same way. It will compare if the value of tryAgain is true or false and if it is true, it will execute the while loop else come out of it

Upvotes: 1

Hassan Naqvi
Hassan Naqvi

Reputation: 423

Closing parentheses are missing for most IF statements. Indent your code properly to find missing parentheses.

Upvotes: 0

ΦXocę 웃 Пepe&#250;pa ツ
ΦXocę 웃 Пepe&#250;pa ツ

Reputation: 48258

if you do this.

while(TryAgain=true){

then your while loop is running for ever...

modify it

Upvotes: 0

MikeCAT
MikeCAT

Reputation: 75062

Change while(TryAgain=true) to while(TryAgain) so that true won't be assigned to TryAgain there and have the while statement see the value of TryAgain.

Upvotes: 3

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