An enum with behaviour in Java
Java interview exercise on Records, classes & interfaces, 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 enum Op with constants ADD, SUB and MUL, each carrying its symbol ("+", "-", "*"), a method apply(a, b) that computes the operation, and a static fromSymbol(s) that finds the constant for a symbol or throws IllegalArgumentException mentioning the symbol.
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.