Working with Arrays and Collections →mediumMultiple SelectObjective-mapped

1Z0-829 Working with Arrays and Collections Practice Question

Which THREE of the following are valid ways to create a new ArrayList<Integer>? (Select three.)

⚠ Common exam trap

It's easy for candidates to confuse `Arrays.asList` with `ArrayList` and attempt to cast the returned list directly, not realizing it is a different class that cannot be cast to `ArrayList`.

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

✓

new ArrayList<>(Arrays.asList(1,2,3))

`Arrays.asList(1,2,3)` returns a fixed-size `List<Integer>`, and passing it to the `ArrayList` constructor creates a new, mutable `ArrayList<Integer>` containing the same elements. This is a standard way to initialize an `ArrayList` with known values.

Answer analysis

Option-by-option breakdown

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

✓
new ArrayList<>(Arrays.asList(1,2,3))
Why this is correct
Creates an ArrayList from the List returned by Arrays.asList.
✗
new ArrayList<>(10, 20, 30)
Why it's wrong here
No constructor takes varargs of elements; this is invalid syntax.
✓
new ArrayList<>(List.of(1,2,3))
Why this is correct
Creates an ArrayList with elements 1,2,3 from an immutable list.
✗
(ArrayList<Integer>) Arrays.asList(1,2,3)
Why it's wrong here
Casting to ArrayList fails at runtime because Arrays.asList returns a java.util.Arrays.ArrayList (a private inner class) not java.util.ArrayList.
✓
new ArrayList<Integer>() with initial capacity 10
Why this is correct
Creates an empty ArrayList with initial capacity 10.

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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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