Java Program to Check Palindrome or Not

This article is created to cover multiple programs in Java that checks whether a number or string is a palindrome number/string or not. The two programs covered in this article are:

  • Java Program to Check Palindrome Number or Not
  • Java Program to Check Palindrome String or Not

Note - A number whose reverse is equal to the number itself, is called a palindrome number. For example, 12321, 121, 1001 etc. are palindrome numbers.

Note - A string whose reverse is equal to the original string, is called as a palindrome string. For example, radar, madam, refer, level, reviver etc. are all palindrome strings.

Check Palindrome Number in Java

The question is, write a Java program to check whether a given number is a palindrome number or not. The number must be received by user at run-time of the program. The program given below is its answer:

import java.util.Scanner;

public class CodesCracker
{
   public static void main(String[] args)
   {
      int num, rev=0, rem, temp;
      Scanner scan = new Scanner(System.in);
      
      System.out.print("Enter a Number: ");
      num = scan.nextInt();
      
      temp = num;
      while(temp!=0)
      {
         rem = temp%10;
         rev = (rev*10) + rem;
         temp = temp/10;
      }
      
      if(num==rev)
         System.out.println("\nIt is a Palindrome Number.");
      else
         System.out.println("\nIt is not a Palindrome Number.");
   }
}

The snapshot given below shows the sample run of above Java program on checking whether a given number is a palindrome number or not, with user input 12321:

java check palindrome number

The above program can also be created in this way:

import java.util.Scanner;

public class CodesCracker
{
   public static void main(String[] args)
   {
      int rev=0;
      Scanner scan = new Scanner(System.in);
      
      System.out.print("Enter a Number: ");
      int num = scan.nextInt();
      
      int temp = num;
      while(temp!=0)
      {
         rev = (rev*10) + (temp%10);
         temp /= 10;
      }
      
      if(num==rev)
         System.out.println("\n" +num+ " is a Palindrome Number.");
      else
         System.out.println("\n" +num+ " is not a Palindrome Number.");
   }
}

Here is its sample run with user input 1245

check palindrome number program java

Check Palindrome String in Java

The question is, write a Java program to check whether a string entered by user at run-time, is a palindrome string or not. The program given below is its answer:

import java.util.Scanner;

public class CodesCracker
{
   public static void main(String[] args)
   {
      String str, strReverse="";
      char ch;
      int i, strLen;
      Scanner scan = new Scanner(System.in);
      
      System.out.print("Enter the String: ");
      str = scan.nextLine();
      
      strLen = str.length();
      i = (strLen-1);
      while(i>=0)
      {
         ch = str.charAt(i);
         strReverse = strReverse + ch;
         i--;
      }
      
      if(str.equals(strReverse))
         System.out.println("\n\"" +str+ "\" is a Palindrome String.");
      else
         System.out.println("\n\"" +str+ "\" is not a Palindrome String.");
   }
}

The sample run of above program with user input radar is shown in the snapshot given below:

java check palindrome string

Same Program in Other Languages

Java Online Test


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