In practice, which is the better default for a general-purpose list: ArrayList or LinkedList?

Options

1. LinkedList, because it is always faster for every operation
2. ArrayList: fast index access and compact in memory (Correct option)
3. They behave exactly the same in speed and memory
4. LinkedList, because it is thread-safe and ArrayList is not

Answer

ArrayList: fast access by index and compact in memory; LinkedList is rarely better

Why

ArrayList stores items in a resizable array: get(i) is instant (O(1)), appending is fast, and items sit together in memory, which CPUs like.

LinkedList stores each item in a separate node with links. Insertion in the middle is only cheap if you already hold the position; finding it takes O(n), and each node costs extra memory.

Use ArrayList by default, and ArrayDeque when you need a queue or stack.

Remember

Default to ArrayList.

Key terms

• ArrayList
• Linked list
• Big-O notation
• Index
• ArrayDeque
• CPU