Translate an exception in Java
Java interview exercise on Exceptions & validation, 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 class ConfigException extends RuntimeException (constructors for a message, and for a message with a cause) and loadPort(env) that reads "PORT" from the map: missing → ConfigException("PORT is missing"); not a number → ConfigException("PORT must be a number, got <value>") with the NumberFormatException as its cause; otherwise the port as an int.
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.