Try It Yourself - SyntaxStudy Editor

HTML / CSS / JS

import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

public class MapSetDemo {
    public static void main(String[] args) {
        // --- HashMap ---
        Map<String, Integer> scores = new HashMap<>();
        scores.put("Alice", 95);
        scores.put("Bob",   87);
        scores.put("Carol", 92);
        scores.put("Alice", 98); // overwrites previous value

System.out.println("Scores: " + scores);
        System.out.println("Alice's score: " + scores.get("Alice"));
        System.out.println("Contains Bob: " + scores.containsKey("Bob"));

// Iterating entries
        System.out.println("
All entries:");
        for (Map.Entry<String, Integer> entry : scores.entrySet()) {
            System.out.printf("  %-6s -> %d%n", entry.getKey(), entry.getValue());
        }

// getOrDefault
        int dave = scores.getOrDefault("Dave", 0);
        System.out.println("Dave's score (default 0): " + dave);

// --- HashSet ---
        Set<String> fruits = new HashSet<>();
        fruits.add("Apple");
        fruits.add("Banana");
        fruits.add("Apple"); // duplicate, ignored
        fruits.add("Cherry");

System.out.println("
Fruits set: " + fruits);
        System.out.println("Contains Banana: " + fruits.contains("Banana"));
        fruits.remove("Banana");
        System.out.println("After remove:    " + fruits);
    }
}