Java Fundamentals · Arrays & Collections · Lesson 18 of 22
HashMap: Key-Value Pairs
Concept
HashMap: Key-Value Pairs
A HashMap stores key-value pairs, similar to a dictionary, letting you look up a value quickly by its key instead of by position.
By the end of this lesson
- Explain the core idea behind HashMap: Key-Value Pairs.
- Predict output before running a change.
- Test one realistic and one unusual input.
- Use the result to make the next decision.
How to study this page
- 1. Read one concept.
- 2. Change the example.
- 3. Run, compare, and explain.
- 4. Complete the challenge below.
Self-check before continuing
Without looking at the example, describe what changes when you modify one input in HashMap: Key-Value Pairs. Then reopen the editor and prove your explanation with a small test.
You are ready to continue when you can predict, test, and explain the result.
Your turn
Create a HashMap mapping course names to their difficulty level, then print one value.
Need a nudge?
Ask about this lesson or your next move. The guide explains the path without taking the work away from you.
Ready for the next lesson?
Mark this lesson complete when you have finished the exercise.
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