1Z0-819 Collections Framework 2

Question 1

Which method in the `List` interface returns an unmodifiable view of the list in Java 11?

Accepted Answer

Collections.unmodifiableList(list)

Answer

`Collections.unmodifiableList()` wraps an existing list in an unmodifiable view, while `List.copyOf()` creates a new independent unmodifiable copy.

Question 2

What happens when you call `Map.entry(key, value)` in Java 11 and then try to call `setValue()` on the returned entry?

Accepted Answer

It throws UnsupportedOperationException

Answer

`Map.entry()` returns an immutable `Map.Entry`, so calling `setValue()` throws `UnsupportedOperationException`.

Question 3

Which `NavigableMap` method returns the greatest key strictly less than the given key, or null if there is no such key?

Accepted Answer

lowerKey()

Answer

`lowerKey(k)` returns the greatest key strictly less than `k`, while `floorKey(k)` returns the greatest key less than or equal to `k`.

Question 4

Which of the following correctly describes the behavior of `LinkedHashMap` regarding iteration order?

Accepted Answer

Iterates in insertion order by default

Answer

`LinkedHashMap` maintains a doubly-linked list to preserve insertion order (or access order if constructed with `accessOrder=true`).

Question 5

What is the return type of `Collections.frequency(Collection<?> c, Object o)`?

Accepted Answer

int

Answer

`Collections.frequency()` returns a primitive `int` representing the number of times the specified element appears in the collection.

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