Collections in Java: interview exercises

Collections in Java: 6 test-checked interview exercises (Remove duplicates, keep the order), each beside a worked example, with tests as you go. Free.

1. Remove duplicates, keep the order
2. Group words by length
3. Balanced brackets
4. The k largest numbers
5. An LRU cache
6. Merge two count maps

Each exercise pairs a worked example with a twin problem to solve in a real editor; the tests run the moment you do. Interview mode hides the example: solve it from memory, without the hint or the solution, and it counts as solved cold. Progress is saved in your browser, and in your account if you sign in.

More Java topics

• Strings
• Streams & lambdas
• Records, classes & interfaces
• Generics & Optional
• Exceptions & validation
• Algorithms & recursion
• Modern Java

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