Java HashMap

Java HashMap

In Java, HashMap is a part of the java.util package and provides a data structure that stores key-value pairs. It allows you to store elements based on unique keys and retrieve them quickly using those keys. Here's a basic overview of how to use HashMap:

        import java.util.HashMap;
import java.util.Map;

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

        // Add key-value pairs to the HashMap
        map.put(1, "Apple");
        map.put(2, "Banana");
        map.put(3, "Orange");

        // Access elements in the HashMap
        System.out.println("Elements in the HashMap:");
        for (Map.Entry entry : map.entrySet()) {
            System.out.println("Key: " + entry.getKey() + ", Value: " + entry.getValue());
        }

        // Get the size of the HashMap
        int size = map.size();
        System.out.println("Size of the HashMap: " + size);

        // Remove a key-value pair from the HashMap
        map.remove(2);

        // Check if a key exists in the HashMap
        boolean containsKey = map.containsKey(3);
        System.out.println("HashMap contains key 3: " + containsKey);

        // Check if a value exists in the HashMap
        boolean containsValue = map.containsValue("Banana");
        System.out.println("HashMap contains value 'Banana': " + containsValue);

        // Clear all key-value pairs from the HashMap
        map.clear();

        // Check if the HashMap is empty
        boolean isEmpty = map.isEmpty();
        System.out.println("HashMap is empty: " + isEmpty);
    }
}
      

This example demonstrates creating a HashMap, adding key-value pairs to it, accessing elements, getting the size, removing key-value pairs, checking if a key or value exists, clearing the HashMap, and checking if it's empty. HashMap provides many more methods for manipulation and retrieval of key-value pairs.