1Z0-819 Lambda Expressions 5

Question 1

Which of the following describes an 'effectively final' variable in the context of lambda capture?

Accepted Answer

A variable whose value is never changed after its initial assignment

Answer

Effectively final means a variable that could have been declared final because it is never reassigned after initialization, even without the explicit final keyword.

Question 2

What is the difference between a lambda expression and an anonymous class instance in Java?

Accepted Answer

Lambdas do not introduce a new scope for 'this'; anonymous classes do.

Answer

Inside a lambda, 'this' refers to the enclosing instance; inside an anonymous class, 'this' refers to the anonymous class instance itself.

Question 3

Which built-in functional interface accepts an int and returns an int without boxing?

Accepted Answer

IntUnaryOperator

Answer

IntUnaryOperator's applyAsInt(int) method accepts and returns a primitive int, avoiding autoboxing overhead.

Question 4

Given: BiFunction<String, Integer, String> f = (s, n) -> s.repeat(n); what does f.apply("ab", 3) return?

Accepted Answer

ababab

Answer

String.repeat(n) repeats the string n times, so "ab".repeat(3) returns "ababab".

Question 5

What is printed by: Supplier<Double> s = Math::random; System.out.println(s.get() == s.get());

Accepted Answer

true or false depending on random values

Answer

Each call to s.get() invokes Math.random() independently, so the two values are extremely unlikely to be equal but could theoretically be.

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

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

1Z0-819 Lambda Expressions 5