Question

\( { Palindromes })\) A palindrome is a sequence of characters that reads the same backward as forward. For example, each of the following five-digit integers is a palindrome: 12321,55555,45554 and \(11611 .\) Write an application that reads in a five-digit integer and determines whether it is a palindrome. If the number is not five digits long, display an error message and allow the user to enter a new value.

Short answer

Check if the number is 5 digits long and compare first with last digit, and the second with the fourth digit for palindromes.

Step-by-step solution

Input Validation

First, we need to ensure that the user enters a valid five-digit integer. If the input is not five digits long, display an error message and prompt the user to enter the number again.

Extract Digits

Assuming the number is a valid five-digit integer, extract each digit to compare them. Let the number be represented as ABCDE, where A, B, C, D, E are individual digits.

Compare Digits

Check if the first digit A is equal to the last digit E and the second digit B is equal to the fourth digit D. This ensures that the number reads the same backward as forward.

Conclusion

If both digit comparisons are true, the number is a palindrome. If either comparison fails, the number is not a palindrome.

Key concepts

Palindrome algorithm

A palindrome algorithm is a sequence of technical steps designed to determine whether a sequence of characters forms a palindrome. In the context of Java programming, this involves operations specific to checking numerical palindromes. A typical numeric palindrome is any number that reads the same forwards and backwards, like 12321.

To implement a palindrome algorithm, follow these key steps:

• Read the input number that could potentially be a palindrome.
• Verify the structure of the number to qualify it as a proper candidate for checking (e.g., ensure it's a five-digit number if required in the problem statement).
• Extract the necessary digits to perform the verification.
• Compare the appropriate digits to determine if they mirror each other across the number's center.
• Return a determination – is it a palindrome or not?

By effectively following the algorithm, you can accurately identify whether a given integer qualifies as a palindrome, a useful skill in many programming contexts.

Input validation

Input validation is a critical aspect of programming that ensures users provide input in an accepted and expected format. In the case of our palindrome problem, it's pivotal to ensure that the user inputs a five-digit integer. This type of validation guards against errors and bugs, ensuring the program runs smoothly.

Here are some steps to ensure clean input validation:

• Check Length: Ensure the number has exactly five digits. Using simple mathematical calculations or string methods can help verify this.


• Error Message: Provide a clear and understandable error message when input does not meet the criteria. Suggest what the user should do next.


• Re-prompt: Allow the user to attempt input again until a valid input is obtained. This can be done using loops like 'while' or 'do-while'.

Thorough input checking not only guides users correctly but also prevents runtime errors and crashes.

Error handling

Error handling is an essential technique in software development. It allows a program to continue running even when encountering unexpected situations. In the Java programming language, great tools exist to detect and resolve issues.

In our palindrome algorithm, error handling is closely tied to input validation. Here's how it can be incorporated effectively:

• Exception Handling: Use try-catch blocks to gracefully handle input-related problems, such as when attempting to convert a non-numeric string to an integer.


• Messages: Display informative error messages that help users understand what went wrong and how to fix it.


• Loop Control: Keep the user in a re-prompting loop until they provide valid input, recovering from failed attempts efficiently.

By incorporating sound error handling strategies, applications remain robust and user-friendly, increasing overall reliability.

Digit extraction

Digit extraction is crucial when working with numerical data, and it's an integral part of determining if a number is a palindrome. Understanding how to isolate digits allows programmers to perform necessary comparisons.

Here’s a simple way to perform digit extraction in Java:

• Using Mathematics: Conduct operations such as digit division and modulo to isolate each digit from a multi-digit number. For example, with the number 12345:
  • A can be found using integer division by 10000.
  • E can be obtained using the modulus operator: number % 10.


• Using Strings: Convert the number to a string to access each character directly. This can sometimes be simpler and more intuitive.

Effective digit extraction gives you the digits needed to complete the palindrome check, facilitating correct logical comparisons.

Conditional logic

Conditional logic is foundational in programming and is crucial in applying the palindrome algorithm efficiently and accurately. Conditional statements allow you to execute code based on the truthfulness of specified conditions.

Within our palindrome task, key comparisons are performed using conditional logic:

• Digit Comparison: Ensure that the first digit equals the last, and the second digit equals the fourth. In Java, these are often executed using 'if' statements: \[\text{If } A == E \text{ and } B == D, \text{ then it is a palindrome}\]


• Execution Path: Based on the result of conditions, direct the program to either declare the number a palindrome or not, sending appropriate messages.

By mastering conditional logic, you can devise efficient algorithms that handle decision-making processes effectively, crucial in not just palindrome detection, but across all forms of logic-based programming.