Working with Arrays and Collections →mediumMultiple ChoiceObjective-mapped

1Z0-829 Working with Arrays and Collections Practice Question

A TreeSet<String> is used to store a list of employee names. The set currently contains "Alice", "Bob", "Charlie". What is the output after calling set.add("Bob")?

⚠ Common exam trap

Candidates often confuse the return value of add() with the behavior of a List, expecting an exception or a successful insertion, but the Set interface mandates that duplicates are silently rejected by returning false.

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

✓

false

A TreeSet implements the Set interface, which does not allow duplicate elements. When calling add("Bob") on a TreeSet that already contains "Bob", the add method returns false, indicating that the element was not added, and the set remains unchanged.

Answer analysis

Option-by-option breakdown

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

✗
Exception
Why it's wrong here
Adding a duplicate does not throw an exception; it simply returns false.
✓
false
Why this is correct
TreeSet implements Set, which does not allow duplicates; add returns false.
✗
The set becomes ["Alice","Bob","Bob","Charlie"]
Why it's wrong here
Sets cannot contain duplicate elements.
✗
true
Why it's wrong here
false is returned because "Bob" already exists.

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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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