Overview of Java TreeMap

A TreeMap is an integral part of Java's Collections Framework, utilized for storing key-value pairs in a sorted order. It implements the NavigableMap interface and is based on a Red-Black tree structure.

Key Features of TreeMap

• Sorted Order: The entries in a TreeMap are sorted based on the natural ordering of its keys or by a specified comparator.
• Null Keys: TreeMap does not permit null keys, although it allows multiple null values.
• Performance: It provides O(log n) time complexity for fundamental operations such as add, remove, and contains.

Important Methods

Here are some essential methods available in the TreeMap class:

• put(K key, V value): Adds a key-value pair to the map.
• get(Object key): Retrieves the value associated with a specific key.
• remove(Object key): Deletes the key-value pair for the specified key.
• containsKey(Object key): Checks if the TreeMap contains a particular key.
• firstKey(): Returns the first (lowest) key in the map.
• lastKey(): Returns the last (highest) key in the map.
• size(): Returns the number of key-value pairs in the map.

Example Usage

Here’s a simple example to illustrate how to use a TreeMap in Java:

import java.util.TreeMap;

public class Example {
    public static void main(String[] args) {
        // Creating a TreeMap
        TreeMap<String, Integer> map = new TreeMap<>();

        // Adding key-value pairs
        map.put("Alice", 30);
        map.put("Bob", 25);
        map.put("Charlie", 35);

        // Accessing a value
        System.out.println("Alice's age: " + map.get("Alice")); // Output: 30

        // Removing a key-value pair
        map.remove("Bob");

        // Checking the size
        System.out.println("Size of map: " + map.size()); // Output: 2

        // Iterating over the TreeMap
        for (String key : map.keySet()) {
            System.out.println(key + ": " + map.get(key));
        }
    }
}

Conclusion

A TreeMap is a valuable data structure when the need arises to maintain a collection of key-value pairs in a sorted format. It offers efficient performance for various operations and is an excellent choice for applications that require ordered data.