Frequently Asked Java Program 03: Java Program to check if any string is palindrome Using inbuilt Reverse method of Java

Hello Folks,

As part of Frequently Asked Java Programs In Interviews For Freshers And Experienced, in this post we will see a Java program to verify if a given string is palindrome using inbuilt reverse method.

WHAT IS PALINDROME STRING?

A palindromic string is a string that remains the same when its characters are reversed.

For Example: NAAN, AMMA etc.

Logic:

Java provides two classes StringBuilder and StringBuffer who has reverse() method. Note here that String class has no reverse method.
We can convert any string to StringBuilder or StringBuffer using their constructors.
There is a trick to compare content of two objects of StringBuffer or StringBuilder which is discussed in below program.

Java Program:

package JavaPrograms;

import java.util.Scanner;

public class PalindromeCharStringUsingStringBuffer {
 public static void main(String[] args) {

  // Taking input from user
  Scanner sc = new Scanner(System.in);
  System.out.println("Please enter the string to know palindrome:");
  String inputByUser = sc.nextLine();
  
  //Converting String in to StringBuilder
  StringBuilder strOriginal = new StringBuilder(inputByUser);
  
  // reversing string
  StringBuilder strReverse = new StringBuilder(strOriginal).reverse();
  
  //since stringBuildr/Buffer do not override equals method so it will not check content
  //To verify content we can use valueOf method of String class. This method class toString() internally.
  if (String.valueOf(strOriginal).equals(String.valueOf(strReverse)))
   System.out.println("Result:Palindrome");
  else
   System.out.println("Result:Not Palindrome");
  
  //Another way to verify content  using toString()
  if ((strOriginal.toString()).equals(strReverse.toString()))
   System.out.println("Result:Palindrome");
  else
   System.out.println("Result:Not Palindrome");
  
  //Using compareTo method
  if ((strOriginal.toString()).compareTo(strReverse.toString()) == 0)
   System.out.println("Result:Palindrome");
  else
   System.out.println("Result:Not Palindrome");


 }
}

package JavaPrograms;

import java.util.Scanner;

public class PalindromeCharStringUsingStringBuffer {

public static void main(String[] args) {

// Taking input from user

Scanner sc = new Scanner(System.in);

System.out.println("Please enter the string to know palindrome:");

String inputByUser = sc.nextLine();

//Converting String in to StringBuilder

StringBuilder strOriginal = new StringBuilder(inputByUser);

// reversing string

StringBuilder strReverse = new StringBuilder(strOriginal).reverse();

//since stringBuildr/Buffer do not override equals method so it will not check content

//To verify content we can use valueOf method of String class. This method class toString() internally.

if (String.valueOf(strOriginal).equals(String.valueOf(strReverse)))

System.out.println("Result:Palindrome");

else

System.out.println("Result:Not Palindrome");

//Another way to verify content using toString()

if ((strOriginal.toString()).equals(strReverse.toString()))

System.out.println("Result:Palindrome");

else

System.out.println("Result:Not Palindrome");

//Using compareTo method

if ((strOriginal.toString()).compareTo(strReverse.toString()) == 0)

System.out.println("Result:Palindrome");

else

System.out.println("Result:Not Palindrome");

}

Output:

Please enter the string to know palindrome:
AMMA
Result:Palindrome
Result:Palindrome
Result:Palindrome

Please enter the string to know palindrome:
NANA
Result:Not Palindrome
Result:Not Palindrome
Result:Not Palindrome

Please enter the string to know palindrome:
AMMA AMMA
Result:Palindrome
Result:Palindrome
Result:Palindrome

You can run above program for multiple inputs and if it fails for any condition, let me know.

#HappyCoding

Author: Amod Mahajan

My name is Amod Mahajan and I am an IT employee with 4+ years of experience in Software testing and staying in Bengaluru. My area of interest is Automation testing. I started from basics and went throw so many selenium tutorials. Thanks to Mukesh Otwani as his tutorials are easy and cover basics to advance. I have habit of exploring concepts by deep diving. I used to make notes. I thought of sharing my knowledge through posts and now I am here. #KeepLearning #ShareLearning

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