Managing Unique Elements with HashSet

In this problem: You will create a program using HashSet<String> to manage a name list, confirming that duplicate additions are ignored, while checking element existence, getting size, and displaying all elements.

Learning Objective: Understand basic operations of HashSet (add, search, size retrieval) as part of the collection framework

Overview

HashSet is a collection that does not allow duplicates. Even if the same element is added multiple times, only one instance is kept. Its key feature is fast element lookup (O(1) average).

Specifications

• Create a HashSet<String>
• Add "Alice", "Bob", "Alice", "Charlie" in order ("Alice" is added twice)
• Print "Size: " + set size
• Print "Contains Alice: " + result of contains("Alice")
• Print "Contains Dave: " + result of contains("Dave")
• Print "--- All names ---"
• Convert to TreeSet and print elements in sorted order, one per line

Output Format

Size: 3
Contains Alice: true
Contains Dave: false
--- All names ---
Alice
Bob
Charlie