LoopExample.java

import java.util.Scanner;

/**
 * Identifies a scenario that may require two different types of loops.
 */
public class LoopExample {

    /**
     * This method demonstrates a scenario where two different types of loops are used.
     * The do-while loop gets user input and keeps looping until the user enters 'exit'.
     * The for each loop is used to iterate over each character in the input string to validate it is a digit.
     *
     * @param args Console arguments. Not used in this example.
     */
    public static void main(String[] args) {

        // Initialize variables.
        // The Scanner is used to read user input.
        // The input is stored in the 'input' variable.
        // The input will be 'valid' if it is a positive integer.
        Scanner scanner = new Scanner(System.in);
        String input;
        boolean valid = false;

        // A do-while loop loops until the condition in the while statement is false.
        // In Java, an exclamation mark (!) means NOT.
        do {
            // Prompt the user to enter a positive integer.
            System.out.print("Enter a positive integer (or 'exit' to quit): ");

            // Get the input from the user and store it in the 'input' variable.
            input = scanner.nextLine();

            // If the input is 'exit', break out of the do-while loop.
            if (input.equalsIgnoreCase("exit")) {
                break;
            }

            // This is a for each loop, which iterates over each character in the input string.
            // Checks if each character in the input is a digit [0-9]
            // If it is not, print an error message and sets 'valid' to false, so it won't try to multiply the number.
            for (char chr : input.toCharArray()) {

                // Set valid to true. If all characters in the input are digits, it will remain true.
                valid = true;

                // If any character in the input is not a digit, print an error message and set 'valid' to false.
                // Break out of the for-each loop immediately if input contains non-digits.
                if (!Character.isDigit(chr)) {
                    System.out.println("Invalid input. Please enter a positive integer.");
                    valid = false;
                    break;
                }
            }

            // If the input is valid, convert it to a float.
            // Print the parsed number divided by 10.
            if (valid) {

                // Convert the input to a float.
                float number = Float.parseFloat(input);

                // Print the input number divided by 10.
                System.out.printf("The number divided by 10 is: %.1f%n", number / 10);
            }

            // This line continues to loop the do-while loop unless the input is 'exit'.
        } while (!input.equalsIgnoreCase("exit"));
        scanner.close();

        // Prints some end-of-program stuff.
        System.out.println("\nThank you for using the divide by ten system. Goodbye!");
        System.out.println("Please leave a rating of your experience in a brief 30 minute survey.");
        System.out.println("We're duped into thinking these surveys give us good, mine-able data.");
    }

}