List

A List is an ordered collection that allows duplicates and positional (indexed) access. Use ArrayList by default; LinkedList only for rare cases where you insert/remove at both ends frequently.

Common operations

List<String> list = new ArrayList<>();
list.add("Ada");
list.add("Grace");
list.add(0, "Alan");   // insert at index 0
list.get(1);            // "Ada"
list.set(1, "Ada Lovelace");
list.remove("Grace");
list.size();            // 2
list.indexOf("Ada Lovelace"); // 1

Immutable lists

List<Integer> ints = List.of(1, 2, 3);  // Java 9+, immutable
// ints.add(4); → UnsupportedOperationException

ArrayList vs LinkedList

In practice, ArrayList wins 95% of the time thanks to CPU cache locality.