Lambdas

Question 1

Can lambdas be generic?

Answer 1

No, but the functional interfaces they implement can be generic

Question 2

What is a lambda expression?

Answer 2

A lambda expression is an anonymous method used to implement the abstract method of a functional interface

Question 3

What is a functional interface?

Answer 3

A functional interface is an interface with only one abstract method

Question 4

Is it possible to explicitly specify the type of a parameter in a lambda expression?

Answer 4

Yes, but is it not necessary since the parameter type can be inferred from the functional interface

Question 5

True or False

When a block lambda seems overly long to embed in a method call, it is possible to assign that lambda to a functional interface variable. Then, you can simply pass that reference to the method

Answer 5

True

Question 6

When is a lambda expression instantiated?

Answer 6

Whenever it is assigned to a funtional interface type

Question 7

Can a lambda expression modify the local variables of its enclosing scope?

Answer 7

No. The local variables of a lambda’s enclosing scope should be effectively final.

For example, the following code is illegal:

Supplier<Integer> incrementor(int start) {
  return () -> start++;
}

Question 8

What are the 4 main functional interfaces provided by java and their associated abstract methods?

Answer 8

1. void Consumer.accept(T t)
2. R Function.apply(T t)
3. boolean Predicate.test(T t)
4. T Supplier.get()