Java Collections Framework

import java.util.*;
import java.util.stream.Collectors;

public class CollectionsDemo {
    public static void main(String[] args) {
        // ArrayList - ordered, allows duplicates
        List<String> fruits = new ArrayList<>(Arrays.asList("Apple", "Banana", "Cherry"));
        fruits.add("Date");
        fruits.remove("Banana");
        System.out.println(fruits);

        // HashMap - key-value pairs
        Map<String, Integer> scores = new HashMap<>();
        scores.put("Alice", 95);
        scores.put("Bob", 87);
        scores.put("Charlie", 92);

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

        // Stream API
        List<String> filtered = fruits.stream()
            .filter(f -> f.startsWith("A"))
            .map(String::toUpperCase)
            .sorted()
            .collect(Collectors.toList());
        System.out.println(filtered);
    }
}