How is ArrayList structured?

ArrayList is a dynamic array that automatically expands when elements are added. It is based on a regular fixed-size array. When the array is filled, a new, larger array is created, and all elements are copied into it.

Main characteristics:

• Fast access by index (O(1))
• Adding at the end — amortized O(1)
• Inserting or deleting in the middle — O(n) due to shifting elements

Example in Java:

ArrayList<String> list = new ArrayList<>();
list.add("apple");
list.add("banana");
System.out.println(list.get(1)); // banana