Practice HashMap - 15.5.2.1 | 15. Collections and Generics | Advanced Programming
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HashMap

15.5.2.1 - HashMap

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Learning

Practice Questions

Test your understanding with targeted questions

Question 1 Easy

What is a HashMap?

💡 Hint: Think about collections that store pairs.

Question 2 Easy

Can a HashMap have a null key?

💡 Hint: Consider how many null values a HashMap can store.

4 more questions available

Interactive Quizzes

Quick quizzes to reinforce your learning

Question 1

What type of collection is a HashMap?

Ordered
Unordered
Sorted

💡 Hint: Think about the nature of HashMap organization.

Question 2

True or False: HashMap allows multiple null keys.

True
False

💡 Hint: How many null keys can you have in a HashMap?

1 more question available

Challenge Problems

Push your limits with advanced challenges

Challenge 1 Hard

Write a Java program that creates a HashMap to store employee names and IDs, then prints each employee's details using entrySet() method.

💡 Hint: Remember to import java.util.HashMap first!

Challenge 2 Hard

Compare the performance of a HashMap versus a TreeMap for inserting 1000 elements. What observations can you make?

💡 Hint: Set up a timer to measure insertion times.

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Reference links

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