AP Computer Science A:: Arraylist

What is the KEY ADVANTAGE of an \(ArrayList\) over a regular array?

- **A)** ArrayLists are always faster than arrays for every operation
- **B)** An \(ArrayList\) always uses less memory than an array
- **C)** An \(ArrayList\) can store primitive types directly, unlike arrays
- **D)** An \(ArrayList\) can DYNAMICALLY grow or shrink in size as elements are added or removed, unlike a regular array, which has a FIXED size once created

Which line of code correctly declares and creates an empty \(ArrayList\) meant to hold \(String\) objects?

- **A)** \(ArrayList\textless String\textgreater\ list\ =\ new\ ArrayList\textless String\textgreater();\)
- **B)** \(ArrayList\ list\ =\ new\ String[10];\)
- **C)** \(ArrayList\textless String\textgreater\ list\ =\ new\ String();\)
- **D)** \(String\ list\ =\ new\ ArrayList();\)

Why can an \(ArrayList\) NOT be declared to hold primitive types directly, such as \(ArrayList\textless int\textgreater\)?

- **A)** ArrayLists cannot store numeric data of any kind
- **B)** \(ArrayList\textless int\textgreater\) is perfectly valid Java syntax with no issues
- **C)** Java's generic types (like \(ArrayList\)) can only work with OBJECT/reference types, not primitives -- so a WRAPPER CLASS (like \(Integer\) for \(int\)) must be used instead: \(ArrayList\textless Integer\textgreater\)
- **D)** This restriction only applies to \(double\), never to \(int\)

What does \(list.add("apple")\) do when called on an \(ArrayList\textless String\textgreater\ list\)?

- **A)** It removes "apple" from the list
- **B)** It replaces the list's ENTIRE contents with just "apple"
- **C)** It appends "apple" to the END of the list, increasing the list's size by 1
- **D)** It checks whether "apple" is already in the list, without modifying it

What does \(list.add(0,\ "apple")\) do, using the TWO-argument version of \(add\)?

- **A)** It appends "apple" to the end of the list, ignoring the index argument entirely
- **B)** It replaces whatever was previously at index 0 with "apple", without shifting anything
- **C)** It INSERTS "apple" at INDEX 0 (the beginning of the list), shifting all existing elements one position to the RIGHT (each existing element's index increases by 1)
- **D)** It removes the element currently at index 0

What does \(list.get(2)\) return for an \(ArrayList\textless String\textgreater\)?

- **A)** The element at the very END of the list, regardless of size
- **B)** The element currently stored at INDEX 2 (the third element, using zero-based indexing, just like arrays)
- **C)** It removes and returns the element at index 2
- **D)** The total number of elements in the list

What does \(list.set(2,\ "banana")\) do?

- **A)** It appends "banana" to the end of the list
- **B)** It removes the element at index 2 without replacing it
- **C)** It REPLACES the element currently at index 2 with "banana", WITHOUT changing the list's overall size
- **D)** It INSERTS "banana" at index 2, shifting later elements to the right (like \(add\))

What is the crucial difference in BEHAVIOR between \(list.set(index,\ value)\) and \(list.add(index,\ value)\)?

- **A)** \(set\) always increases the list's size, while \(add\) never does
- **B)** \(set\) REPLACES an existing element in place (size stays the same), while \(add\) INSERTS a new element and SHIFTS all subsequent elements over (size increases by 1)
- **C)** \(add\) can only be used to remove elements, never to insert them
- **D)** \(set\) and \(add\) always behave identically