Welcome! Today, we're exploring the dynamic world of HashMaps in Java. It's part of the Java Collections framework, designed for efficient data storage and retrieval. Imagine a HashMap as a locker system in a spaceship, where each locker (i.e., a key) can store an item (i.e., a value). In this lesson, we'll construct a HashMap, add key-value pairs, access elements, and understand the basic properties and methods.

Ready? Let's go!

Creating a HashMap involves declaring its data type and initializing it. Just like an ArrayList, HashMaps can only hold object types. Here's a HashMap that maps our spaceship crew's names (String) to their ages (Integer).

The HashMap is empty for now, represented by {}.

In our spaceship, different crew members have different roles. These roles can be linked to the crew members' ages.