Question

Write a method that takes an integer value and returns the number with its digits reversed. For example, given the number 7631, the method should return 1367. Incorporate the method into an application that reads a value from the user and displays the result.

Short answer

Define a method 'reverseDigits' to reverse the digits of an integer. Create a main application to take user input, call 'reverseDigits', and display the reversed number.

Step-by-step solution

Create the Method to Reverse Digits

Define a method called 'reverseDigits' that takes an integer parameter. Inside the method, initialize an integer variable 'reversed' to store the reversed number. Use a 'while' loop that runs as long as the input is not zero. Inside the loop, calculate the remainder when the number is divided by 10 (which gives the last digit), multiply 'reversed' by 10 and add the remainder to 'reversed', then divide the number by 10 to remove the last digit. Continue the loop until the number becomes zero.

Incorporate the Method into an Application

Create a main application in which you can test the 'reverseDigits' method. Prompt the user to enter an integer. Store the user input in a variable. Call the 'reverseDigits' method with the user input as the argument and assign the result to another variable. Output the result to the console.

Testing the Application

Run the application and enter the number 7631 when prompted. Verify that the output displayed is 1367, which confirms that the method is working correctly.

Key concepts

reverseDigits

The 'reverseDigits' method embodies a simple yet elegant algorithmic approach to invert the order of digits in a given integer. Imagine you have a number like 7631; this method will transform it into 1367. The beauty of this method lies in its simplicity and efficiency.

First off, initializing a variable, let's name it 'reversed', to store the reverse of the input number is crucial. As the 'while' loop iterates, a pivotal operation takes place—extracting the last digit of the number using the modulus operator (the number % 10). This digit is then added to 'reversed', which is simultaneously being built up by multiples of 10. Think of it as shifting digits to the left in 'reversed' to make room for the new ones. After snagging the digit, you systematically strip it from the original number by division (number /= 10).

It's the looping and the shuffling of digits within these steps that bring 'reversed' to life, imparting it digit by digit with those of the original number—only, well, reversed. Each operation is crucial, and altering the sequence could lead to incorrect results or even an infinite loop—one certainly to be avoided.

while loop

The 'while' loop in Java is a fundamental control structure that's perfect for when you're not quite sure how many times you'll need to loop. In the context of the 'reverseDigits' method, it shines as it persistently runs as long as the condition 'number != 0' holds true.

The construct of a 'while' loop is straightforward: it begins with the keyword 'while', followed by a condition within parentheses, and enclosed within braces is the block of code to execute as long as the condition is met. In every iteration, the reverseDigits method ensures the integer's last digit is peeled off and correctly placed at the end of the reversed integer. This loop acts like a diligent miner, extracting digit by digit until there's nothing left to mine.

It's crucial to ensure that the loop's condition will eventually be false; otherwise, you'll be caught in an endless whirl of iterations—a bug known as an infinite loop. Proper implementation of this loop within 'reverseDigits' method guarantees that the number keeps getting smaller until it's finally whittled down to zero.

console input/output

In Java, console input and output are the means through which a user may interact with an application via text. User input is typically gathered using a `Scanner` object, which can read various data types from the console. The method 'reverseDigits' we discussed earlier would need a user's number to begin its digit-flipping magic. That's where console input comes into play. The application prompts the user with a message, waits for a response, and once the user submits their number, the magic happens.

The output part is equally intuitive—the system outputs a statement, in our case, the reversed integer, back to the user through a method such as ‘System.out.println()’. This simple back-and-forth exchange allows for dynamic code testing where the user can actively verify if 'reverseDigits' indeed performs as intended. Keeping these interactions clear, concise, and instructive ensures that the user remains engaged and not confused by what's asked or what the given response signifies.