Java program to check String is a palindrome or not
Check whether a String is Palidrome
In this article we will see if the string is palindrome or not in java programming language.
A string is palindrome if the reverse and the original string is same
Lets understand this with the help of an example:-
- Input sting:- AMA
- Reverse sting:- AMA
Here AMA = AMA so this is a palindrome
Algorithm
- Take a String input from user and store it in a variable called “s”
- Take a variable called as “rev” to store reverse value
- Take a i loop and start it from i=s.length()-1 to i>=0
- Then get each character one by one using charAt() and store it in “rev” variable
- If rev variable is equals to s variable then print String is palindrome else print String is not palindrome
Code in Java
Run
import java.util.Scanner; public class StringIsAPalindromeOrNot { public static void main(String[] args) { String s = "arora"; String rev = ""; for (int i = s.length()-1; i >=0 ; i--) rev=rev+s.charAt(i); if(s.equals(rev)) System.out.println("String is palindrome"); else System.out.println("String is not palindrome"); } }
Output
String is palindrome
Note
In this java program, we’re going to check string input by the user will be palindrome or not. Take a String input from the user and store it in a variable called “s”. A palindrome string is one that will be the same if we read from forward and from backward also. Strings like ‘madam’, ‘lol’, ‘pop’, ‘arora’ are examples of palindrome string . We’re storing a reversed string in ‘rev’ variable after that we will compare that original string and the reversed string are same or not using equals() method.
Method 2 (Check whether a String is Palidrome)
Here the reverse of the string will be stored and then will be checking if the original and the reverse is same or not.
Run
import java.util.*;
public class Main {
public static void main(String args[]) {
String original = "Prepinsta", reverse = ""; // Objects of String class
int length = original.length();
for (int i = length - 1; i >= 0; i--)
reverse = reverse + original.charAt(i);
if (original.equals(reverse))
System.out.println("Entered string is a palindrome.");
else
System.out.println("Entered string isn't a palindrome.");
}
}
Output
Entered string isn't a palindrome.
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public static void main(String[] args) {
String str=”racecar”;
int n=str.length()/2;
int count=0;
for (int i=0;i<n;i++){
if(str.charAt(i)!=str.charAt(str.length()-1-i)){
System.out.println("Not palindrome");
count++;
break;
}
}
if(count==0){
System.out.println("Palindrome");
}
}
import java.util.*;
class HelloWorld {
public static void main(String[] args) {
Scanner sc=new Scanner(System.in);
String s=sc.nextLine();
String rev=””;
for(int i=s.length()-1;i>=0;i–){
char c=s.charAt(i);
rev+=c;
}
if(s.equals(rev)){
System.out.print(“Yes”);
return;
}
else{
System.out.print(“NO”);
}
}
}
import java.util.Scanner;
public class String2 {
public static void main(String[] args){
Scanner sc = new Scanner(System.in);
String s = sc.next();
StringBuilder rev = new StringBuilder();
for(int i = s.length()-1; i>=0; i–){
rev.append(s.charAt(i));
}
if(s.equalsIgnoreCase(rev.toString())){
System.out.println(“Palindrome”);
}
else
System.out.println(“not palindrome”);
}
}
public static void isPalindrome(String str) {
boolean sub=true;
int i=0;
int j=str.length() – 1;
while(i < j){
if(str.charAt(i)!=str.charAt(j)){
sub=false;
break;
}
i++;
j–;
}
if(sub){
System.out.println("The entire String is palindrome");
}
else{
System.out.println("The entire String is not palindrome");
}
}
public class Main {
public static void main(String[] args){
System.out.println(“enter a string”);
Scanner sc=new Scanner(System.in);
String s= sc.next();
int i,j;
for(i=0,j=s.length()-1;ij)
System.out.println(“palidrome”);
else
System.out.println(“not palidrome”);
}
}
public class Main
{
public static void main(String[] args) {
String str=”aroora”;
int n=str.length();
boolean isPalindrome=true;
for(int i=0;i<n/2;i++){
if(str.charAt(i)!=str.charAt(n-i-1)){
isPalindrome=false;
break;
}
}
if(isPalindrome){
System.out.println("Palindrome");
}else{
System.out.println("Not palindrome");
}
}
}
import java.util.*;
class Baba {
public static boolean isPalindrome(String s, int n) {
int l = 0;int r = n-1;
while(l<=r) {
if(s.charAt(l) != s.charAt(r)) {
return false;
}
l++;
r–;
}
return true;
}
public static void main(String[] agrs) {
Scanner sc = new Scanner(System.in);
System.out.print("Enter a String: ");
String s = sc.next();
int n = s.length();
if(isPalindrome(s, n) == true) {
System.out.println("Palindrome");
} else {
System.out.println("Not a Palindrome String");
}
}
}
package StringProblem;
import java.util.*;
public class chekcStringPalindromORnot {
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
System.out.println(“Enter the string and chekc the string is palindrom or not”);
String s = sc.next();
// using for each loop
String rev = “”;
for(char c : s.toCharArray()) {
rev =c+rev;
}
if(s.equals(rev))
System.out.println(“String is palindrom”);
else
System.out.println(“not palindrom”);
}
}
the shortest solution thank you shubhamm and prep insta
public class JavaApplication1
{
public static void main(String[] args)
{
Scanner obj = new Scanner(System.in);
String s = obj.nextLine();
String c=””;
for(char i : s.toCharArray())
{
c = i + c;
}
if(c.equalsIgnoreCase(s))
System.out.print(“Yes”);
else
System.out.print(“NO”);
}
}
This can be optimesed as
j =str1.length()-1;
for( i=0; i<str1.length(); i++ )
{
if( str1.charAt(i) != str1.charAt(j) // i is moving from left to right whereas j from right to left
return false;
j–;
}
return true ; // for palindrome