Question

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's 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

To determine if a five-digit integer is a palindrome, validate its length, convert to a string, compare corresponding characters and display whether it is a palindrome or not.

Step-by-step solution

Obtain the Integer

Prompt the user to enter a five-digit integer and store the input in a variable.

Validate the Length of the Integer

Check if the length of the integer is exactly five digits long. If it's not, display an error message and prompt the user to enter a new value.

Convert Integer to String

Since checking for a palindrome involves reversing the order of characters, convert the integer to a string to facilitate character-wise comparison.

Check for Palindrome

Compare the first character with the last, the second character with the second-last, and so on. If all corresponding characters match, the integer is a palindrome.

Display the Result

If the integer is a palindrome, display a message confirming it. If it's not, indicate that it's not a palindrome.

Key concepts

Java Programming

Java is a widely-used programming language that allows developers to create robust and multi-platform applications. In the context of our palindrome detection exercise, Java provides the tools needed to both interact with the user and process the information given. When asking for user input, Java utilizes classes such as Scanner from the java.util package, which enables the program to read numbers, strings, and other data types from various inputs, including the console.

For instance, obtaining the integer from a user requires the following code snippet:

Scanner scanner = new Scanner(System.in);
int number = scanner.nextInt();

This simple interaction is a fundamental Java programming concept when dealing with console-based user inputs.

Subsequently, the logic for verifying whether the input is indeed a five-digit integer, alongside the palindrome evaluation, is achieved through a series of conditional statements and string manipulations. These are exemplary of Java's capability to handle both numerical computations and character processing effectively.

Integer Validation

The integral validation process starts immediately after the user's input. Since the palindrome we're interested in must be a five-digit number, the program needs to ensure that the user input conforms to this constraint before proceeding with any further computations. In Java, this can be handled as follows:

if(String.valueOf(number).length() != 5) {
   System.out.println('Error: Input is not a five-digit integer.');
   // prompt the user to enter a new value
}

Notice that we convert the integer to a String to check its length, leveraging Java's built-in String.valueOf() method. This conversion simplifies checking the number of digits in the integer since strings are arrays of characters in Java. If the length is not equal to 5, an error message is shown. This validation is critical because it ensures that the logic applied afterward, for palindrome-checking, is executed on appropriate data.

String Manipulation

Once the integer passes validation, the next step of the algorithm involves string manipulation. The program must convert the integer into a string to assess whether it is a palindrome. The palindrome check then compares characters at symmetrical positions in the string—a concept easily implemented via string manipulation tasks.

To illustrate, here's how you might flip a string in Java and compare it to the original:

String originalNumber = String.valueOf(number);
String reversedNumber = new StringBuilder(originalNumber).reverse().toString();
if(originalNumber.equals(reversedNumber)) {
   System.out.println('The number is a palindrome.');
} else {
   System.out.println('The number is not a palindrome.');
}

Incorporating the StringBuilder class for reversing the string is a testament to Java's comprehensive standard libraries that simplify many common programming tasks such as string reversal.

The use of these manipulation strategies bypass the need for more complex array handling or manual index-based character checking, making the code more concise and understandable. Effective string manipulation is at the heart of numerous algorithms and is a skill any proficient Java programmer should possess.