Arrays & Collections

1public class ArrayDemo {
2    public static void main(String[] args) {
3        // Declaration and initialization
4        int[] numbers = {10, 20, 30, 40, 50};
5 
6        // Access by index
7        System.out.println(numbers[0]); // 10
8        System.out.println(numbers.length); // 5
9 
10        // Loop through array
11        for (int num : numbers) {
12            System.out.print(num + " ");
13        }
14        // Output: 10 20 30 40 50
15    }
16}

1import java.util.ArrayList;
2import java.util.HashMap;
3 
4public class CollectionsDemo {
5    public static void main(String[] args) {
6        // ArrayList
7        ArrayList<String> skills = new ArrayList<>();
8        skills.add("Java");
9        skills.add("Python");
10        skills.add("SQL");
11        System.out.println(skills); // [Java, Python, SQL]
12 
13        // HashMap
14        HashMap<String, Integer> scores = new HashMap<>();
15        scores.put("Alice", 95);
16        scores.put("Bob", 88);
17        System.out.println(scores.get("Alice")); // 95
18    }
19}