Unchecked call to 'lambda(T, T)' as a member of raw type 'my.lambda.closure'

Question

While practicing Labdas, I am passing Lambdas from my main methods. It runs alright, but IntelliJ shows warning saying that: Unchecked call to 'lambda(T, T)' as a member of raw type 'my.lambda.closure' at line 18. What am I missing here?

package my.lambda;

interface Closure<T extends Number> {
    boolean lambda(T a, T b);
}

class Collection<T extends Number> {
    private T[] numbers;

    Collection(T[] numbers) {
        this.numbers = numbers;
    }

    T getDesired(Closure closure) {
        T desiredSoFar = numbers[0];

        for (T number : numbers) {
            if (closure.lambda(number, desiredSoFar))
                desiredSoFar = number;
        }

        return desiredSoFar;
    }
}

public class Lambda {
    public static void main(String[] args) {
        Integer[] iOb = {1, 2, 3, 12, 4, 5, 6};
        Collection<Integer> integerCollection = new Collection<>(iOb);

        Double max = integerCollection.getDesired((a, b) -> a.doubleValue() > b.doubleValue())
                .doubleValue();
        Double min = integerCollection.getDesired((a, b) -> a.doubleValue() < b.doubleValue())
                .doubleValue();

        System.out.println("Maximum of the integers: " + max);
        System.out.println("Maximum of the integers: " + min);

        Double[] dOb = {1.1, 2.2, 3.3, 12.12, 4.4, 5.5, 6.6};
        Collection<Double> doubleCollection = new Collection<>(dOb);

        max = doubleCollection.getDesired((a, b) -> a.doubleValue() > b.doubleValue());
        min = doubleCollection.getDesired((a, b) -> a.doubleValue() < b.doubleValue());

        System.out.println("Maximum of the doubles: " + max);
        System.out.println("Maximum of the doubles: " + min);
    }
}

Answer 1

You have defined Closure here as a raw type.

T getDesired(Closure closure) 

What you intended might be

T getDesired(Closure<T> closure) 

There is a built in closure called BiPredicate which tests a pair of values.

BTW, max and min should be Integer, I wouldn't change them to Double

Integer max = integerCollection.getDesired((a, b) -> a > b);