findPalindromeNumbersInRange()

Step 1:

The first step is to build a base function that checks if a given number is a palindrome. This will be done by converting the number into a string and then comparing this string with its reverse.

public static boolean isPalindrome(int number) {
    String numberAsString = String.valueOf(number);
    return numberAsString.equals(new StringBuilder(numberAsString).reverse().toString());
}

Step 2:

The next step is to use the isPalindrome function within a loop that goes through the specified range of numbers and adds any numbers that return true from the isPalindrome function to a list.

public static List<Integer> findPalindromesInRange(int start, int end) {
    List<Integer> palindromes = new ArrayList<Integer>();
    for (int i = start; i <= end; i++) {
        if (isPalindrome(i)) {
            palindromes.add(i);
        }
    }
    return palindromes;
}

Step 3:

Now that we have the base function ready, it's time to implement the rest of the functionality. The function findPalindromesInRange simply iterates from start to end inclusive and checks if the current number is a palindrome using the function isPalindrome(). If it is, the number is added to the list of palindrome numbers.

Step 4:

It's time to test our code! We can test it by using some known ranges that should contain palindromes. For example, testing the code with the range from 10 to 200 should return [11, 22, 33, 44, 55, 66, 77, 88, 99, 101, 111, 121, 131, 141, 151, 161, 171, 181, 191].

Step 5: The final step

In conclusion, our Java function successfully checks a given range for palindrome numbers. It does so by first checking if a number is a palindrome, before then iterating over the specified range and adding any palindrome numbers to a list. Here is our full code.

public class Main {

    public static boolean isPalindrome(int number) {
        String numberAsString = String.valueOf(number);
        return numberAsString.equals(new StringBuilder(numberAsString).reverse().toString());
    }

    public static List<Integer> findPalindromesInRange(int start, int end) {
        List<Integer> palindromes = new ArrayList<Integer>();
        for (int i = start; i <= end; i++) {
            if (isPalindrome(i)) {
                palindromes.add(i);
            }
        }
        return palindromes;
    }

    public static void main(String[] args) {
        System.out.println(findPalindromesInRange(10, 200));
    }
}