Question

Write an application that inputs one number consisting of five digits from the user, separates the number into its individual digits and prints the digits separated from one another by three spaces each. For example, if the user types in the number 42339, the program should print Assume that the user enters the correct number of digits. What happens when you enter a number with more than five digits? What happens when you enter a number with fewer than five digits? [Hint: It’s possible to do this exercise with the techniques you learned in this chapter. You’ll need to use both division and remainder operations to “pick off” each digit.]

Short answer

To separate a five-digit number, use division and modulus operations to extract and then print each digit with three spaces in between. Numbers with more or less than five digits need to be handled specifically by prompting for correct input or adjusting the input number.

Step-by-step solution

Input Validation

Start by creating a method to read the user's input. Validate the input to ensure it is exactly five digits long. If not, prompt the user again or handle the error according to your application's requirements.

Separate the Digits

Use division and remainder operations to extract each digit from the number. To get each digit, you can repeatedly divide and find the remainder by 10. For instance, the last digit is obtained by calculating the remainder of the number divided by 10.

Store and Display the Digits

Starting with the rightmost digit, store each digit in a variable or an array. Then print the digits separated by three spaces each.

Handling More Than Five Digits

If a number with more than five digits is inadvertently entered, the method should print an error message or prompt the user to enter exactly five digits.

Handling Fewer Than Five Digits

If a number fewer than five digits is entered, the method should either warn the user and request a five-digit number or prepend zeros to the number until it is five digits long, then separate and print the digits.

Key concepts

Input Validation

In any application where user input is required, validating this input is crucial to ensure that the data complies with the expected format or range.
For the Java digit separation task, input validation involves checking that the entered number is exactly five digits long. Here's how you can improve on this specific validation process:

• Use a while loop that continues to prompt the user until a valid number is entered.
• Within the loop, use a condition to check if the input has exactly five digits by verifying that the number lies between 10000 (smallest five-digit number) and 99999 (largest five-digit number), both inclusive.
• If the check fails, inform the user of the specific issue, either being too short or too long, and prompt for re-entry.

This approach not only guides the user but also prevents the application from proceeding with invalid data that could potentially cause errors or unexpected behavior later in the process.

Division and Remainder Operations

Separating a number into its individual digits is a common task in programming, frequently achieved using division and remainder operations.

• To isolate the last digit, we use the remainder operation (also known as the modulus operation), indicated by the symbol '%'. For example, the expression \( 42339 \% 10 \) would evaluate to 9.
• To remove the last digit from the number, we divide the number by 10. Noting that Java truncates the result when dividing integers, \( 42339 / 10 \) will yield 4233.

By repeatedly applying these operations, we can pick off each digit starting from the rightmost one. A key improvement is to store these digits in an array, which can then be indexed to print the digits in the desired format. This orderly method allows for easy access to each digit for further processing if needed.

Error Handling

Error handling is a defensive programming technique that anticipates potential issues and defines how the application should respond whenever an exceptional or unexpected situation arises.
In our Java digit separation exercise, error handling ensures that the application behaves sensibly when a user enters a number with more or fewer than five digits. To enhance the robustness of your application, consider implementing these tips:

• For numbers with more than five digits, provide a clear error message that instructs the user on the required number of digits and allows them to try again.
• When fewer than five digits are entered, automatically padding the number with leading zeros can correct the mistake. Alternatively, you can prompt the user to retry with the correct format.
• Ensure to catch exceptions that might occur during the input process, such as non-numeric characters being entered, and guide the user to correct the mistake.

These practices not only make your application user-friendly but also prevent crashes or unexpected results, thereby enhancing user trust in the application's reliability.