Working with Arrays and Collections →hardMultiple SelectObjective-mapped

1Z0-829 Working with Arrays and Collections Practice Question

Which TWO statements about the java.util.Collections class are true?

⚠ Common exam trap

It's easy for candidates to confuse mutating methods like sort, reverse, and shuffle with methods that return new collections, when in fact these methods modify the list in place and return void, whereas synchronizedList and unmodifiableList return wrapper views.

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

✓

Collections.synchronizedList(List) returns a synchronized list backed by the specified list.

Collections.synchronizedList(List) returns a synchronized (thread-safe) list backed by the specified list. This method wraps the provided list in a synchronized wrapper, ensuring that all access to the underlying list is serialized when accessed through the returned list. It does not create a new independent list but provides a view that synchronizes all method calls.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

✗
Collections.sort(List) returns a new sorted list.
Why it's wrong here
Collections.sort sorts the list in place; it does not return a new list.
✗
Collections.reverse(List) returns a new reversed list.
Why it's wrong here
Collections.reverse reverses the order in place.
✗
Collections.shuffle(List) returns a new shuffled list.
Why it's wrong here
Collections.shuffle randomizes the list in place.
✓
Collections.synchronizedList(List) returns a synchronized list backed by the specified list.
Why this is correct
It returns a thread-safe list backed by the specified list.
✓
Collections.unmodifiableList(List) returns an unmodifiable view of the specified list.
Why this is correct
It returns an unmodifiable view; any attempt to modify it throws UnsupportedOperationException.

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1Z0-829 Working with Arrays and Collections Practice Question

Why each option matters

Option-by-option breakdown

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