Java program to check Palindrome string using lambda expression

Last update on March 11 2025 14:01:31 (UTC/GMT +8 hours)

Check if String is Palindrome

Write a Java program to implement a lambda expression to check if a given string is a palindrome.

Sample Solution:

Java Code:

import java.util.function.Predicate;

public class Main {
  public static void main(String[] args) {
    // Define the palindrome check lambda expression
    Predicate < String > isPalindrome = str -> {
      String reversed = new StringBuilder(str).reverse().toString();
      return str.equals(reversed);
    };

    // Check if a string is a palindrome using the lambda expression
    String word1 = "Madam";
    boolean isPalindromeResult1 = isPalindrome.test(word1);
    System.out.println(word1 + " is a palindrome? " + isPalindromeResult1);

    String word2 = "radar";
    isPalindromeResult1 = isPalindrome.test(word2);
    System.out.println(word2 + " is a palindrome? " + isPalindromeResult1);

    String word3 = "defied";
    isPalindromeResult1 = isPalindrome.test(word3);
    System.out.println(word3 + " is a palindrome? " + isPalindromeResult1);
  }
}

Sample Output:

Madam is a palindrome? false
radar is a palindrome? true
defied is a palindrome? false

Explanation:

In the above exercise -

• From the java.util.function package, we import Predicate.
• In the main method, we define a lambda expression str -> { ... } to check if a string is a palindrome.
• Inside the lambda expression, we create a reversed version of the input string by using a StringBuilder to reverse the characters. We convert it back to a string using toString().
• Compare the original string with the reversed string using the equals() method. Return true if they are equal, indicating that the string is a palindrome. Otherwise, it returns false.
• Create an instance of the Predicate interface called isPalindrome and assign the lambda expression to it.
• Test the lambda expression by checking some strings are palindromes or not using the test() method on the isPalindrome predicate.

Flowchart:

For more Practice: Solve these Related Problems:

• Write a Java program to implement a lambda expression that checks if a string is a palindrome by reversing it and comparing.
• Write a Java program to create a lambda that checks palindromicity of a string ignoring case and non-alphanumeric characters.
• Write a Java program to implement a lambda that returns true if every word in a sentence is a palindrome.
• Write a Java program to chain lambda expressions to filter out palindromic strings from a list.

Live Demo:

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