Treemap in Java

The Treemap is a part of the Java Collections Framework and is an implementation of the SortedMap interface. It maintains its elements in a sorted order based on the natural ordering of keys or a specified comparator.

Usage of Treemap

To use a Treemap, you need to import the java.util.TreeMap class:

import java.util.TreeMap;

Then, you can create a new instance of Treemap using its default constructor or providing a custom comparator if needed:

 // Default constructor - sorts elements based on natural ordering of keys
        TreeMap<Integer, String> treeMap = new TreeMap<>();

// Using a custom comparator for sorting elements
        TreeMap<String, Integer> customTreeMap = new TreeMap<>((a, b) -> b.compareTo(a));

Adding and Accessing Elements

You can add elements to the Treemap using the put() method, and retrieve elements using the get() method:

 treeMap.put(1, "One");
        treeMap.put(2, "Two");
        treeMap.put(3, "Three");

        String value = treeMap.get(2); // Returns "Two"
        System.out.println("Value at 2 = "+value);

Iterating through Treemap

You can iterate through the elements of a Treemap using various methods, such as keySet(), entrySet(), or values():

       // Using keySet()
        for (Integer key : treeMap.keySet()) {
            String value1 = treeMap.get(key);
            System.out.println(key + " = " + value1);
        }

// Using entrySet()
        for (Map.Entry<Integer, String> entry : treeMap.entrySet()) {
            System.out.println(entry.getKey() + " -> " + entry.getValue());
        }

// Using values()
        for (String value1 : treeMap.values()) {
            System.out.println(value1);
        }

Other Useful Methods

The Treemap class provides many useful methods, including size(), containsKey(), containsValue(), remove(), firstKey(), lastKey(), and more. Make sure to check the Java documentation for a complete list of available methods.

Conclusion

In this article, we covered the basics of using Treemap in Java. It's a powerful data structure that allows you to store and access elements in sorted order based on keys. Remember to explore the Java documentation for a deeper understanding of the available methods and functionalities of the Treemap class.