Question

public interface UnaryPredicate<T> {
    public boolean test(T obj);
}

This is a functional interface and can therefore be used 
as the assignment target for a lambda expression or method reference.

Q2: Write a class Primepredicate to implement the UnaryPredicate interface where
T is Integer class. In the class, override the test method returns true if the argument 
is a palindrome number (for example: 101, 53035)
  
Q3: Write a generic method to count the number of elements 
in a collection that have a specific property 
(for example, odd integers, prime numbers, palindromes).


Q4: Test your generic method in a demo program.

Answer 1

Below is your code: -

import java.util.Arrays;
import java.util.Collection;

class Primepredicate implements UnaryPredicate<Integer> {
   public boolean test(Integer i) {
       String numToStr = i.toString();
       int length = numToStr.length();
       String rev = "";
       for (int j = length - 1; j >= 0; j--)
           rev = rev + numToStr.charAt(j);

       return rev.equals(numToStr);
   }
}

class PredicateFunction {
   public static <T> int countIfTrue(Collection<T> collect, UnaryPredicate<T> predicate) {

       int count = 0;
       for (T item : collect) {
           if (predicate.test(item)) {
               ++count;
           }
       }
       return count;
   }
}

public class DemoTester {
   public static void main(String[] args) {
       Collection<Integer> collectionToTest = Arrays.asList(101, 102, 3023, 53035);
       int count = PredicateFunction.countIfTrue(collectionToTest, new Primepredicate());
       System.out.println("Number of palindrome numbers = " + count);
   }
}