Milline on erinevus Java kogumite Set ja ArrayList kogumite rakendamisel?

The main difference between the collections Set and ArrayList in Java lies in their behavior and implementation:

• Set — is a collection that does not allow duplicates. The order of elements is not guaranteed (for example, in HashSet), although there are implementations with ordering (TreeSet, LinkedHashSet).
• ArrayList — is an ordered list that allows duplicates and preserves the insertion order.

From an implementation perspective:

• ArrayList is based on an array that dynamically expands when elements are added. Fast access by index.
• HashSet is usually implemented on top of HashMap, where elements act as keys. This ensures fast search and uniqueness check.

Example:

Set<String> set = new HashSet<>();
set.add("apple");
set.add("apple"); // will not be added a second time

List<String> list = new ArrayList<>();
list.add("apple");
list.add("apple"); // both elements will be added