Pattern matching for switch in Java
Java interview exercise on Modern Java, difficulty 2 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 describe(o) as a switch over an Object with type patterns: null → "nothing"; an Integer above 100 → "big number" (a guard with when); any other Integer → "number <n>"; a String → "text of length <n>"; a List → "list of <size>"; anything else → "something".
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.