Palindrome
A palindrome is a word, number, phrase, or other sequence of characters which reads the same backward as forward, such as madam or racecar or the number 10801.
For more information:
Palindrome checker in Java
Upasana | July 24, 2020 | 2 min read | 1,394 views | Java Coding Challenges
Palindrome checker in Java
In simple words, A Palindrome Number is a number that even when reversed is same as original number.
Pseudo code
So our approach will be quite simple:
-
Get the input number and copy it in temporary variable
-
Reverse the original number
-
Compare if the temporary number is same as the reversed number
-
If both are same then input is a palindrome else not
Let’s write the implementation in java.
Palindrome Checker
public class Palindrome {
boolean isPalindrome(int input) {
int reversed = reverse(input);
return input == reversed;
}
private int reverse(int input) {
int lastDigit, sum = 0, temp;
temp = input;
while (temp > 0) {
lastDigit = temp % 10; (1)
sum = (sum * 10) + lastDigit;
temp = temp / 10;
}
return sum; (2)
}
}| 1 | We are using remainder operator to get the last digit of number |
| 2 | sum is the reversed number |
JUnit testcase
We can write simple JUNIT testcase to assert that basic functionality of palindrome checker program.
Few testcases, that we can think of:
-
check a palindrome number
-
check a non-palindrome number
-
check zero as the input
-
check for negative numbers
JUnit Testcase
import org.junit.jupiter.api.Test
import org.junit.jupiter.api.Assertions.*
import org.junit.jupiter.api.assertThrows
class PalindromeNumberCheckerTest {
@Test
fun `check a palindrome number`() {
val checker = PalindromeNumberChecker()
assertEquals(true, checker.isPalindrome(1001))
}
@Test
fun `check a non-palindrome number`() {
val checker = PalindromeNumberChecker()
assertEquals(false, checker.isPalindrome(12))
}
@Test
fun `check if zero is palindrome`() {
val checker = PalindromeNumberChecker()
assertEquals(true, checker.isPalindrome(0))
}
@Test
fun `check negative numbers`() {
val checker = PalindromeNumberChecker()
val exception = assertThrows<AssertionError> {
checker.isPalindrome(-100)
}
assertEquals("input must be positive number", exception.message)
}
}That’s all!
| Here we are only considering integers for Palindrome, but the same logic can be applied to any other input type (word, phrase, etc) |
|
Did you know?
The longest palindromic word in the Oxford English Dictionary is the onomatopoeic tattarrattat, coined by James Joyce in Ulysses (1922) for a knock on the door
|
If you are looking for more complex example, where we do the bit wise reversal of a number to check if it is palindrome or not, follow this article:
For String input, you can refer to Check if a given String is palindrome
You can download sample project from Github
https://github.com/cancerian0684/junit5-gradle-kotlin-sample
Java Coding Challenges:
- Reverse position of words in a string using recursion
- Check if the given string is palindrome
- Find two numbers of which the product is maximum in an array
- Prime number checker in Java
- Create anagram buckets from a given input array of words
- Anagrams string checker in Java
- Reverse a string using recursion in Java
Top articles in this category:
- Check if the given string is palindrome
- 50 Java Interview Questions for SDET Automation Engineer
- Java Coding Problems for SDET Automation Engineer
- Anagrams string checker in Java
- Junit interview questions for SDET automation engineer
- Rest Assured API Testing Interview Questions
- Prime number checker in Java
Recommended books for interview preparation:
Book you may be interested in..
Book you may be interested in..
