Introduction
In this article, we will learn how to check palindrome in Java.
A number which is same as its reverse is a Palindrome in Java. Meaning, palindrome number remains same if we reverse the number.


Example of Palindrome Numbers : 121, 343, 23432, 191 etc.
Similarly, A string is said to be a palindrome if it is same as its reverse.
Example of Palindrome Strings : MAM , MADAM , LOL etc.
Algorithm : How to check if a number is Palindrome in Java?
- Take the Number.
- Store the Number in Temp variable.
- Reverse the Number.
- Compare the Temp Number with the Reversed Number.
- Check if both are same.
- If they are same, Number is Palindrome.
Program : How to check if a number is Palindrome in Java?
There are two ways , we can check if a Number is Palindrome. As mentioned below :
- Using while loop.
- Using for loop.
Example 1: Check Palindrome using while loop
public class CheckPalindrome {
public static void main(String[] args) {
int num = 323, reversedNum = 0, rem, OriginalNum;
OriginalNum = num;
//Loop will run until the "num" does not reaches 0
while( num != 0 )
{
rem = num % 10;
reversedNum = reversedNum * 10 + rem;
num /= 10;
}
// Printing Output
if (OriginalNum == reversedNum){
System.out.println("Number is a Palindrome");
}
else{
System.out.println("Number is not a Palindrome");
}
}
}
As the provided number 323 is a palindrome. Below will be the Output :
Number is a Palindrome
Example 2: Check Palindrome using for loop
public class CheckPalindromeInJava {
public static void main(String[] args) {
int num = 324, reversedNum = 0, rem, OriginalNum;
OriginalNum = num;
for( ;num != 0; num /= 10 )
{
rem = num % 10;
reversedNum = reversedNum * 10 + rem;
}
// Printing Output
if (OriginalNum == reversedNum){
System.out.println("Number is a Palindrome");
}
else{
System.out.println("Number is not a Palindrome");
}
}
}
As the provided number 324 is not a palindrome. Below will be the Output :
Number is not a Palindrome
Algorithm : How to check if a String is Palindrome in Java?
Let’s take a look :
- Take the String.
- Reverse the String and store it in different variable.
- Compare the reversed String with the original String.
- Check if both are same.
- If they are same, String is Palindrome.
Program : How to check if a String is Palindrome in Java?
There are two ways , we can check if a String is Palindrome. As mentioned below :
- Using loop.
- Using Standard library methods. (reverse(), equal() etc.)
Example 1: Check String Palindrome using loop
import java.util.*;
class CheckPalindromeInJava
{
public static void main(String args[])
{
String str , reverse = "";
Scanner in = new Scanner(System.in);
System.out.println("Enter the String to check if it is a palindrome");
str = in.nextLine();
int len = str.length();
for ( int i = len - 1; i >= 0; i-- ) {
reverse = reverse + str.charAt(i);
}
if (str.equals(reverse)) {
System.out.println("String is a Palindrome");
}
else {
System.out.println("String is not a Palindrome");
}
}
}
Input : ABA
Output : String is a Palindrome
Input : HELLO
Output : String is not a Palindrome
Example 2: Check String Palindrome using predefined methods
import java.util.*;
class CheckPalindromeInJava
{
public static void main(String args[])
{
String str , reverse = "";
Scanner in = new Scanner(System.in);
System.out.println("Enter the String to check if it is a palindrome");
str = in.nextLine();
reverse = new StringBuffer(str).reverse().toString();
if (str.equals(reverse)) {
System.out.println("String is a Palindrome");
}
else {
System.out.println("String is not a Palindrome");
}
}
}
Input : MAM
Output : String is a Palindrome
Conclusion
We have learnt different ways of checking the Number and String Palindrome in Java. This is one of the most asked Java interview Question.
Thanks for Reading!