The problem description should be more specific, especially about returned output for a case when a number is not a palindrome, it looks that expected text then is "NOT PALINDROME". It also looks that test cases contain only some small numbers and algorithms do not have to be efficient.

import java.io.; import java.util.; interface PerformOperation { boolean check(int a); } class MyMath { public static boolean checker(PerformOperation p, int num) { return p.check(num); }

public PerformOperation isOdd() { return num -> num % 2 != 0; }

public PerformOperation isPrime() { return num -> (num == 2 || num == 3) || (num % 2 != 0 && num % 3 !=0); }

public PerformOperation isPalindrome() {
    return number -> {
        List<String> strNumber = Arrays.asList(String.valueOf(number).split("")) ;
        Collections.reverse(strNumber);
        int reversedNumber = Integer.parseInt(String.join("",strNumber));
        if (number == reversedNumber)
            return true;
        else
            return false;

    };
}

} // Write your code here

public class Solution {

public static void main(String[] args) throws IOException { MyMath ob = new MyMath(); BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); int T = Integer.parseInt(br.readLine()); PerformOperation op; boolean ret = false; String ans = null; while (T--> 0) { String s = br.readLine().trim(); StringTokenizer st = new StringTokenizer(s); int ch = Integer.parseInt(st.nextToken()); int num = Integer.parseInt(st.nextToken()); if (ch == 1) { op = ob.isOdd(); ret = ob.checker(op, num); ans = (ret) ? "ODD" : "EVEN"; } else if (ch == 2) { op = ob.isPrime(); ret = ob.checker(op, num); ans = (ret) ? "PRIME" : "COMPOSITE"; } else if (ch == 3) { op = ob.isPalindrome(); ret = ob.checker(op, num); ans = (ret) ? "PALINDROME" : "NOT PALINDROME";

} System.out.println(ans); } } }

works well for java 15 import java.util.Scanner;

interface PerformOperation { boolean check(int a); }

class MyMath { // Method to check if the number is odd public static PerformOperation isOdd() { return (int a) -> a % 2 != 0; }

// Method to check if the number is prime
public static PerformOperation isPrime() {
    return (int a) -> {
        if (a <= 1) return false;
        for (int i = 2; i <= Math.sqrt(a); i++) {
            if (a % i == 0) return false;
        }
        return true;
    };
}

// Method to check if the number is a palindrome
public static PerformOperation isPalindrome() {
    return (int a) -> {
        String str = Integer.toString(a);
        String reverseStr = new StringBuilder(str).reverse().toString();
        return str.equals(reverseStr);
    };
}

// Method to execute the operation based on the condition
public static boolean checker(PerformOperation p, int num) {
    return p.check(num);
}

}

public class Solution { public static void main(String[] args) { MyMath math = new MyMath(); Scanner sc = new Scanner(System.in); int T = sc.nextInt();

    while (T-- > 0) {
        int ch = sc.nextInt();
        int num = sc.nextInt();
        PerformOperation op;
        boolean result = false;

        switch (ch) {
            case 1:
                op = MyMath.isOdd();
                result = MyMath.checker(op, num);
                System.out.println(result ? "ODD" : "EVEN");
                break;
            case 2:
                op = MyMath.isPrime();
                result = MyMath.checker(op, num);
                System.out.println(result ? "PRIME" : "COMPOSITE");
                break;
            case 3:
                op = MyMath.isPalindrome();
                result = MyMath.checker(op, num);
                System.out.println(result ? "PALINDROME" : "NOT PALINDROME");
                break;
        }
    }
    sc.close();
}

}