TreeMap and TreeSet in Java

🌳 TreeMap and TreeSet in Java

In the world of Java collections, TreeMap and TreeSet in Java are powerful tools when you need data to be stored in a naturally sorted order. Both are part of the Java Collections Framework and are implemented using Red-Black Trees, ensuring log(n) time complexity for basic operations like insertion, removal, and lookup.

📍 What is TreeMap?

A TreeMap is a map that stores key-value pairs in sorted order according to the keys. It does not allow null keys and uses natural ordering or a specified comparator.

This makes it perfect when you need ordered maps with efficient access.

import java.util.TreeMap;

TreeMap<Integer, String> map = new TreeMap<>();
map.put(3, "C++");
map.put(1, "Java");
map.put(2, "Python");

System.out.println(map); // Outputs: {1=Java, 2=Python, 3=C++}

📌 Features of TreeMap

• Stores key-value pairs in ascending key order
• Does not allow null keys
• Implements NavigableMap and SortedMap
• Supports custom ordering using Comparator

🌿 What is TreeSet?

A TreeSet is a collection that stores unique elements in sorted order. It is ideal when you want to maintain a set of non-duplicate elements in a naturally ordered fashion.

Like TreeMap, TreeSet is based on the Red-Black tree algorithm.

import java.util.TreeSet;

TreeSet<String> set = new TreeSet<>();
set.add("Banana");
set.add("Apple");
set.add("Mango");

System.out.println(set); // Outputs: [Apple, Banana, Mango]

📌 Features of TreeSet

• Stores unique elements in sorted order
• Does not allow null elements (throws exception)
• Implements NavigableSet and SortedSet
• Supports custom comparators for sorting logic

⚙️ Common Methods

• TreeMap: put(), get(), remove(), firstKey(), lastKey()
• TreeSet: add(), remove(), contains(), first(), last()

🚀 When to Use TreeMap or TreeSet?

• Use TreeMap when you need a sorted dictionary-like structure with key-value pairs.
• Use TreeSet when you want to store unique elements in a specific order.
• Both are perfect for range-based operations and ordered traversals.

✅ Conclusion

Understanding how to use TreeMap and TreeSet in Java gives you control over sorted data in your applications.

Whether you're building search indexes, leaderboards, or auto-suggestion features, these sorted structures make your work easier and more efficient.