HackerRank Java Lambda Expressions problem solution

In this HackerRank Java Lambda Expressions problem in the java programming language you need to Write the following methods that return a lambda expression performing a specified action:

1. PerformOperation isOdd(): The lambda expression must return true if a number is odd or false if it is even.
2. PerformOperation isPrime(): The lambda expression must return true if a number is prime or false if it is composite.
3. PerformOperation isPalindrome(): The lambda expression must return true if a number is a palindrome or false if it is not.

HackerRank Java Lambda Expression problem solution.

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);
 }

   PerformOperation isOdd()
   {
       PerformOperation po = (int a)-> a%2 == 0 ? false : true;
       return po;
   }
   PerformOperation isPrime()
   {
       PerformOperation po = (int a)->  
       {
           if(a == 1) return true;
           else
           {
               for (int i =  2; i < Math.sqrt(a); i++)
                    if(a%i == 0) return false;
                return true;
           }
       };
       return po;
   }
   PerformOperation isPalindrome()
   {
       ArrayList<Integer> aa = new ArrayList<>();
       PerformOperation po = (int a)->
       {
            String str = Integer.toString(a);
           String reverse = "";
           for(int i = str.length()-1; i >= 0; i--)
           {
               reverse = reverse + str.charAt(i);
           }
           if(reverse.equals(str)) return true;
           return false;
       };
       return po;
   }
}



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);
  }
 }
}