Implementing And and OR methods in Bifunctions using Generics

Question

I am trying to implement 'and' and 'or' methods in Bifunction the way we have in Predicates.

So, my bifunction functional interface has one abstract method - which takes two objects as arguments and returns a list .

I tried this:

public interface TriFunctionInterface<T, U, R> {
    List<R> applyFilter(T t, U u, List<R> r);
    default TriFunctionInterface or(TriFunctionInterface other) {
        Objects.requireNonNull(other);
        return (T t, U u, List<R> r) -> {
            List<R> finalList = new ArrayList<>();
            List<R> filteredObjects1 = applyFilter(t, u, r);
            List<R> filteredObjects2 = other.applyFilter(t, u, r);
            finalList.addAll(filteredObjects1);
            finalList.addAll(filteredObjects2);
            return finalList;
       };
    }
}

But it seems to be give me an error at this line: 'return (T t, U u, List r) -> {'

Answer 1

it seems to be give me an error

It does give an error, which says:

Error:(11, 16) java: incompatible types: incompatible parameter types in lambda expression. 

This error is caused by the fact that your method uses raw types instead of proper generic types. It should be

default TriFunctionInterface<T, U, R> or(TriFunctionInterface<T, U, R> other)