What is the difference between using TreeSet and TreeMap in Java collections?

TreeSet and TreeMap are collections from Java based on red-black trees, which store elements in sorted order.

• TreeSet is a set that stores unique elements without keys. It is implemented based on TreeMap, where elements act as keys, and default values are a placeholder constant.

• TreeMap is a map that stores key-value pairs, where keys are sorted either by their natural order or with the help of a Comparator.

Summary:

• TreeSet stores only unique elements (as keys), without associating them with any values.
• TreeMap stores key-value pairs, allowing quick lookup of values by key.

Example usage:

TreeSet<String> set = new TreeSet<>();
set.add("apple");
set.add("banana");

TreeMap<String, Integer> map = new TreeMap<>();
map.put("apple", 1);
map.put("banana", 2);