How to directly initialize a HashMap (in a literal way)?

In Java, you can directly initialize a HashMap using its literal syntax by using the curly braces {} and providing key-value pairs separated by commas. Here's an example of how you can do it:

java

import java.util.HashMap;

public class HashMapExample {
    public static void main(String[] args) {
        // Initializing a HashMap using literal syntax
        HashMap<String, Integer> ages = new HashMap<String, Integer>() {
            {
                put("Alice", 25);
                put("Bob", 30);
                put("Carol", 28);
            }
        };

        // Accessing values from the HashMap
        System.out.println("Age of Alice: " + ages.get("Alice"));
        System.out.println("Age of Bob: " + ages.get("Bob"));
        System.out.println("Age of Carol: " + ages.get("Carol"));
    }
}

In this example, we create a HashMap named ages using the literal syntax within curly braces. The key-value pairs are defined inside the curly braces using the put() method. You'll notice that this syntax involves creating an anonymous inner class with an instance initializer block ({}) to achieve the direct initialization.

Please note that while this syntax allows for direct initialization of a HashMap, it might not be the most concise or readable approach, especially for small maps. For larger maps or cases where you want to create a HashMap with a lot of key-value pairs, consider using the regular put() method calls or utilizing a library like Google Guava's ImmutableMap for improved readability.