Java - Use predicate without lambda expressions

Question

I've below requirement:-

Employee.java

public boolean isAdult(Integer age) {
    if(age >= 18) {
        return true;
    }
    return false;
}

Predicate.java

    private Integer age;
Predicate<Integer> isAdult;

public PredicateAnotherClass(Integer age, Predicate<Integer> isAdult) {
    this.age = age;
    System.out.println("Test result is "+ isAdult(age));
}

public void testPredicate() {
    System.out.println("Calling the method defined in the manager class");

}

Now My goal is to test whether the age which i pass to Predicate is adult or not using the method defined in Employee class , for which i am passing the method reference which i pass in the constructor of Predicate class.

But i don't know how to call the method defined in Employee class, below is my test class :-

public class PredicateTest {

    public static void main(String[] args) {
        PredicateManager predicateManager = new PredicateManager();

        PredicateAnotherClass predicateAnotherClass = new PredicateAnotherClass(20, predicateManager::isAdult);
        predicateAnotherClass.testPredicate();;
    }
}

I am getting the compilation error in the System.out.println("Test result is "+ isAdult(age)); in the predicate class.

Let me know how to resolve this issue. and if i need to provide any other information.

Answer 1

Predicate interface has method test(). You should use this method in a following way:

isAdult.test(age)

This method evaluates this predicate on the given argument. It returns true if the input argument matches the predicate, otherwise false