Java Map

Java map

Created By: chatGPT

Java maps are a part of the Java Collections Framework and a type of collection that stores data in key-value pairs. Each key is unique, and it maps to a specific value. Maps are useful for efficiently retrieving data based on specific keys. The most commonly used interfaces for maps in Java are Map, HashMap, TreeMap, and LinkedHashMap. Here's a brief overview of each:

HashMap: This class uses a hash table to implement the Map interface. It is not synchronized, allows null values, and does not guarantee the order of the elements.
TreeMap: Implements the Map interface using a red-black tree. It orders the keys in natural order or by a comparator provided at map creation.
LinkedHashMap: This class maintains a doubly-linked list to preserve the insertion order while using a hash table to store the elements.

Example usage of a HashMap in Java:

import java.util.HashMap;

public class MapExample {
    public static void main(String[] args) {
        // Create a HashMap
        HashMap<String, Integer> map = new HashMap<>();

        // Add elements to the map
        map.put("Alice", 30);
        map.put("Bob", 25);
        map.put("Charlie", 35);

        // Retrieve an element
        int age = map.get("Alice");
        System.out.println("Alice's age: " + age);

        // Check if a key exists
        if (map.containsKey("Bob")) {
            System.out.println("Bob's age is available.");
        }

        // Iterate over the keys
        System.out.println("Map entries:");
        for (String key : map.keySet()) {
            System.out.println(key + " : " + map.get(key));
        }

        // Remove an element
        map.remove("Charlie");
        System.out.println("After removing Charlie: " + map);
    }
}