1Z0-819 Lambda Expressions 4

Question 1

Which of the following lambda expressions is equivalent to the method reference Integer::parseInt?

Accepted Answer

s -> Integer.parseInt(s)

Answer

Integer::parseInt is a static method reference equivalent to the lambda s -> Integer.parseInt(s).

Question 2

A lambda that takes no arguments and returns void corresponds to which functional interface?

Accepted Answer

Runnable

Answer

Runnable's run() method takes no parameters and returns void, making it the natural fit for () -> { ... } style lambdas.

Question 3

What does Function.identity() return?

Accepted Answer

A function that returns its input argument unchanged

Answer

Function.identity() returns a Function that always returns its input argument (t -> t).

Question 4

Given: Predicate isEven = n -> n % 2 == 0; Predicate isPositive = n -> n > 0; which call correctly creates a predicate for even AND positive numbers?

Accepted Answer

isEven.and(isPositive)

Answer

Predicate.and() returns a composed predicate that represents a short-circuit logical AND of both predicates.

Question 5

Which of the following is TRUE about serializing lambda expressions in Java?

Accepted Answer

Lambdas are serializable only if the target functional interface extends Serializable.

Answer

A lambda is serializable if and only if its target type (the functional interface) extends java.io.Serializable.

(1Z0-819) Oracle Java SE 11 Developer Practice Test