Understanding Java Predicates

Question

I have a problem understanding Java Predicates...

Example:

public class UserPredicates {
 public static Predicate<User> isNameEmpty() {
  return p -> p.getFirstName().isEmpty() && p.getLastName().isEmpty();
 }
}

The above example confusing to me, how does it know that p have the method getFirstName() and getLastName() ?
If I understand it correctly, isNameEmpty() returns a function with one parameter ( p ), but does the compiler really figure out the type by looking at the return type?

And the returned function is test() from the Predicate interface?

Answer 1

Predicate<User> means a function that takes a User as its parameter, and returns a boolean .

See Javadoc :

Interface Predicate
...
Type Parameters:
T - the type of the input to the predicate