Array vs ArrayList: Key Differences & When to Use
An Array is a fixed-length, type-safe data structure baked into the language; an ArrayList is a resizable wrapper around an Array provided by the collections framework.
Developers often reach for ArrayList first because “lists” feel friendlier, yet they later hit memory or performance walls—exactly when a plain, predictable Array would have saved the day.
Key Differences
Array: fixed size, faster access, primitive-friendly. ArrayList: dynamic growth, slower index ops, stores only objects, offers add/remove convenience.
Which One Should You Choose?
Use Array when length is known and speed matters; pick ArrayList when you need to insert, delete, or don’t know final size.
Examples and Daily Life
Store chessboard squares in an Array[8][8]; track scrolling chat messages with an ArrayList
Can an ArrayList hold int values?
No, it wraps them into Integer objects; an int[] avoids boxing and uses less memory.
Is ArrayList thread-safe?
Not by default. Use Collections.synchronizedList or CopyOnWriteArrayList for concurrent access.