Painful menstrual periods are periods in which a woman has crampy lower abdominal pain, sharp or aching pain that comes and goes, or possibly back pain. Some pain during your period is normal, but a large amount of pain is not. The medical term for painful menstrual periods is dysmenorrhea.
When an exception occurs, we say that the exception is thrown. For example, we say that Integer.parseInt(str) throws an exception of type NumberFormatException when the value of str is illegal. When an exception is thrown, it is possible to catch the exception and prevent it from crashing the program. This is done with a try..catch statement.
You are throwing an exception that is caused by a usage error (that is, by an error in program logic made by the developer who is calling your method). Typically, you would throw an exception such as ArgumentException, ArgumentNullException, InvalidOperationException, or NotSupportedException.