Java TreeMap: Sorted Key-Value Storage & NavigableMap Operations

TreeMap is an implementation of the NavigableMap and SortedMap interfaces based on a Red-Black Binary Search Tree. Unlike HashMap which stores entries in random hash buckets, TreeMap maintains its keys in guaranteed ascending sorted order.

Code Example: TreeMap in Action

import java.util.TreeMap;

public class TreeMapDemo {
    public static void main(String[] args) {
        // Automatically sorted by alphabetical key order
        TreeMap<String, Double> productPrices = new TreeMap<>();

        productPrices.put("MacBook Pro", 1999.0);
        productPrices.put("AirPods Max", 549.0);
        productPrices.put("iPhone 15", 999.0);
        productPrices.put("iPad Air", 599.0);

        // Keys are sorted alphabetically:
        System.out.println("Sorted Products: " + productPrices);

        // Range Queries (NavigableMap methods):
        System.out.println("First Product: " + productPrices.firstKey()); // AirPods Max
        System.out.println("Last Product:  " + productPrices.lastKey());  // iPhone 15

        // Extracting headMap (keys strictly before "MacBook Pro")
        System.out.println("HeadMap: " + productPrices.headMap("MacBook Pro"));
    }
}

HashMap vs. LinkedHashMap vs. TreeMap