What types of trees are used within the TreeSet data structure?

In Java, the data structure TreeSet is usually implemented based on a balanced tree, most often a Red-Black Tree.

A Red-Black Tree is a type of self-balancing binary search tree that provides insertion, deletion, and search operations in O(log n) time.

Thus, TreeSet stores elements in sorted order and provides efficient access and modification thanks to the use of a Red-Black Tree.

Example of using TreeSet:

TreeSet<Integer> set = new TreeSet<>();
set.add(5);
set.add(1);
set.add(3);
System.out.println(set); // Will output [1, 3, 5]