Set Implementations in Java
Understanding HashSet, LinkedHashSet, and TreeSet
What are Set Implementations?
Set implementations in Java are collections that store unique elements with no duplicates. Each implementation differs in how it orders elements—some maintain no order, others preserve insertion order, and some automatically sort elements. Understanding these differences helps you choose the right Set for your needs.
1
HashSet
Simple explanation
- •Stores items using hashing
- •No specific order (elements appear randomly)
Example
HashSetExample.java
Set<String> set = new HashSet<>();
set.add("Apple");
set.add("Banana");
set.add("Cherry");
System.out.println(set);
// Output might be: [Banana, Cherry, Apple] (order is random)2
LinkedHashSet
Simple explanation
- •Stores items in the order you add them
- •Maintains insertion order
Example
LinkedHashSetExample.java
Set<String> set = new LinkedHashSet<>();
set.add("Apple");
set.add("Banana");
set.add("Cherry");
System.out.println(set);
// Output: [Apple, Banana, Cherry] (same order as inserted)3
TreeSet
Simple explanation
- •Stores items in sorted (ascending) order
- •Uses a Red-Black Tree under the hood
- •Sorting happens automatically
Example
TreeSetExample.java
Set<String> set = new TreeSet<>();
set.add("Cherry");
set.add("Apple");
set.add("Banana");
System.out.println(set);
// Output: [Apple, Banana, Cherry] (sorted alphabetically)Quick Summary
| Set Type | Order of Elements | How It Works |
|---|---|---|
| HashSet | ❌ No order | Hashing |
| LinkedHashSet | ✔ Keeps insertion order | Linked list + Hashing |
| TreeSet | ✔ Sorted order | Red-Black Tree |
Key Differences at a Glance
HashSet
•Fastest performance
•Random order
•Best for lookup
LinkedHashSet
•Predictable order
•Insertion order preserved
•Good for iteration
TreeSet
•Automatically sorted
•Ascending order
•Slower than HashSet