Example: HashMapExample in Java

// HashMapExample
import java.util.HashMap;
import java.util.Map;

// Main class containing the entry point of the program
public class Main {
    public static void main(String[] args) {
        // Step 1: Create a HashMap to store String (key) and Integer (value) pairs
        Map<String, Integer> studentScores = new HashMap<>();
        System.out.println("Initial student scores: " + studentScores);

        // Step 2: Add key-value pairs to the HashMap
        studentScores.put("Alice", 95);
        studentScores.put("Bob", 88);
        studentScores.put("Charlie", 92);
        System.out.println("After adding scores: " + studentScores);

        // Step 3: Retrieve a value using its key
        int aliceScore = studentScores.get("Alice");
        System.out.println("Alice's score: " + aliceScore);

        // Step 4: Check if a key or value exists
        boolean hasBob = studentScores.containsKey("Bob");
        boolean hasScore90 = studentScores.containsValue(90);
        System.out.println("Contains Bob? " + hasBob);
        System.out.println("Contains score 90? " + hasScore90);

        // Step 5: Update a value
        studentScores.put("Bob", 90); // Overwrites Bob's previous score
        System.out.println("After updating Bob's score: " + studentScores);

        // Step 6: Remove a key-value pair
        studentScores.remove("Charlie");
        System.out.println("After removing Charlie: " + studentScores);

        // Step 7: Iterate through key-value pairs
        System.out.println("All scores:");
        for (Map.Entry<String, Integer> entry : studentScores.entrySet()) {
            System.out.println(entry.getKey() + ": " + entry.getValue());
        }
    }
}