How to
find if number is palindrome in Java
Checking whether a number is palindrome or not is a classical Java
homework exercise. When you start learning Java programming most institute
which teach Java programming provides
these classical Java programs like How
to find Armstrong number in Java or how
to find Fibonacci number in Java using recursion etc. Write a Java program to check if number is palindrome comes from same category. For those who are not familiar with
palindrome numbers, palindrome number is a number which is equal to reverse of
itself. For example 121 is a palindrome because reverse of 121 is 121, while
123 is not a palindrome in Java because reverse of 123 is 321 and 121!=321. Finding
palindrome number is easy in Java, you just need to develop logic
to reverse a number in Java. Thankfully Java provides couple of arithmetic
operators like remainder(%) operator also known as modules operator, which
returns remainder in division operator and division operator(/) which returns
quotient. By using remainder and division operator in Java we can create
program to check if number is palindrome or not.
Java program – palindrome numbers in Java
Here is a complete Java program to check if a given number is palindrome
or not, This program works for both positive and negative numbers and display
if its palindrome irrespective of there sign. Any one digit number including
zero is always palindrome. This program is able to check two digit , three
digit numbers for palindrome and effective go to any number in Java. Let’s see
how to write Java program to find palindrome numbers :
package testing;
import java.util.Scanner;
import java.util.Scanner;
/**
* Java program to check if number is palindrome or not.
* A number is called palindrome if number and its reverse is equal
* This Java program can also be used to reverse a number in Java
*/
public class NoClassDefFoundErrorDueToStaticInitFailure {
public static void main(String args[]){
System.out.println("Please Enter a number : ");
int palindrome = new Scanner(System.in).nextInt();
if(isPalindrome(palindrome)){
System.out.println("Number : " + palindrome + " is a palindrome");
}else{
System.out.println("Number : " + palindrome + " is not a palindrome");
}
}
/*
* Java method to check if number is palindrome or not
*/
public static boolean isPalindrome(int number) {
int palindrome = number; // copied number into variable
int reverse = 0;
while (palindrome != 0) {
int remainder = palindrome % 10;
reverse = reverse * 10 + remainder;
palindrome = palindrome / 10;
}
// if original and reverse of number is equal means
// number is palindrome in Java
if (number == reverse) {
return true;
}
return false;
}
}
Output:
Please Enter a number :
123
Number : 123 is not a palindrome
Please Enter a number :
121
Number : 123 is a palindrome
* Java program to check if number is palindrome or not.
* A number is called palindrome if number and its reverse is equal
* This Java program can also be used to reverse a number in Java
*/
public class NoClassDefFoundErrorDueToStaticInitFailure {
public static void main(String args[]){
System.out.println("Please Enter a number : ");
int palindrome = new Scanner(System.in).nextInt();
if(isPalindrome(palindrome)){
System.out.println("Number : " + palindrome + " is a palindrome");
}else{
System.out.println("Number : " + palindrome + " is not a palindrome");
}
}
/*
* Java method to check if number is palindrome or not
*/
public static boolean isPalindrome(int number) {
int palindrome = number; // copied number into variable
int reverse = 0;
while (palindrome != 0) {
int remainder = palindrome % 10;
reverse = reverse * 10 + remainder;
palindrome = palindrome / 10;
}
// if original and reverse of number is equal means
// number is palindrome in Java
if (number == reverse) {
return true;
}
return false;
}
}
Output:
Please Enter a number :
123
Number : 123 is not a palindrome
Please Enter a number :
121
Number : 123 is a palindrome
That’s all on how to check if a number is palindrome or not in Java.
If you are looking answer of this question for interview purpose then better
prepare a recursive version of palindrome program in Java as well because its
common practice that programmer are expected to write java program using both
recursion and iteration in Java. Let me know if you find any other way of
checking palindrome in Java.
Other Java homework programming exercise:
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