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Java program to check whether a string is a Palindrome

  • Difficulty Level : Basic
  • Last Updated : 03 Feb, 2021

Given a string str, the task is to find whether the string is a palindrome or not in Java without using library methods.

Examples:  

Input: str = “abba” 
Output: Yes

Input: str = “geeks” 
Output: No  

Approach: Take two pointers i pointing to the start of the string and j pointing to the end of the string. Keep incrementing i and decrementing j while i < j and at every step check whether the characters at these pointers are same or not. If not then the string is not a palindrome else it is.



Below is the implementation of the above approach: 

Java




// Java implementation of the approach
public class GFG {
 
    // Function that returns true if
    // str is a palindrome
    static boolean isPalindrome(String str)
    {
 
        // Pointers pointing to the beginning
        // and the end of the string
        int i = 0, j = str.length() - 1;
 
        // While there are characters to compare
        while (i < j) {
 
            // If there is a mismatch
            if (str.charAt(i) != str.charAt(j))
                return false;
 
            // Increment first pointer and
            // decrement the other
            i++;
            j--;
        }
 
        // Given string is a palindrome
        return true;
    }
 
    // Driver code
    public static void main(String[] args)
    {
        String str = "geeks";
 
        if (isPalindrome(str))
            System.out.print("Yes");
        else
            System.out.print("No");
    }
}
Output: 
No

 

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