Remove duplicates, keep the order in Java
Java interview exercise on Collections, difficulty 1 of 3. Solve it in the editor beside a worked example, or cold in Interview mode with the example hidden; the tests run the moment you do.
Write dedupe(items) that returns a new list with each value kept only the first time it appears, in the original order. The input list must not be modified. A LinkedHashSet does the remembering and the ordering in one go.
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.