Java Collections Map and Set

Store unique items with HashSet and key-value pairs with HashMap.

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The Java Collections Framework provides core data structures: HashMap offers O(1) average time complexity for key-value retrieval, while HashSet prevents duplicate items.

Key Takeaways: Java Collections Map and Set

Mastering Java Collections Map and Set helps you write clean and reliable Java code. Follow standard conventions, test edge cases, and keep logic simple. Try running the code example below and complete the exercises to build confidence.

Java Collections Map and Set Code Example

Java

import java.util.*;

public class Main {
    public static void main(String[] args) {
        Map<String, Integer> stock = new HashMap<>();
        stock.put("Laptops", 15);
        stock.put("Monitors", 25);
        System.out.println("Laptops in stock: " + stock.get("Laptops"));
    }
}

Output

Laptops in stock: 15

Run this example on your own computer. The "Get Started" lesson shows how to set it up.

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Java Collections Map and Set

💡 Key Takeaways: Java Collections Map and Set

Java Collections Map and Set Code Example

Key Takeaways: Java Collections Map and Set