Java TreeSet: Red-Black Balanced Trees & NavigableSet Operations

TreeSet implements the NavigableSet interface, backed internally by a self-balancing Red-Black Binary Search Tree. It ensures that elements are stored strictly unique and maintained in ascending sorted order.

Code Demonstration: NavigableSet Navigation Methods

import java.util.TreeSet;

public class TreeSetDemo {
    public static void main(String[] args) {
        TreeSet<Integer> numbers = new TreeSet<>();
        numbers.add(50);
        numbers.add(20);
        numbers.add(80);
        numbers.add(10);
        numbers.add(90);

        // Elements automatically sorted: [10, 20, 50, 80, 90]
        System.out.println("Sorted TreeSet: " + numbers);

        // 1. Boundary Queries:
        System.out.println("Smallest (first): " + numbers.first()); // 10
        System.out.println("Largest (last):   " + numbers.last());  // 90

        // 2. NavigableSet Proximity Queries:
        System.out.println("Higher than 50 (strictly >):  " + numbers.higher(50));  // 80
        System.out.println("Lower than 50 (strictly <):   " + numbers.lower(50));   // 20
        System.out.println("Ceiling of 45 (>=):           " + numbers.ceiling(45)); // 50
        System.out.println("Floor of 45 (<=):             " + numbers.floor(45));   // 20

        // 3. SubSet Range Extraction:
        System.out.println("Subset [20 to 80): " + numbers.subSet(20, 80)); // [20, 50]
    }
}

HashSet vs. LinkedHashSet vs. TreeSet