Fausto Spoto wrote:

In general one should not define new instances of RuntimeException but nevermind.

Enea has checked the following document: http://www.j2ee.me/docs/books/tutorial/essential/exceptions/runtime.html Here it is said: Runtime exceptions represent problems that are the result of a programming problem, and as such, the API client code cannot reasonably be expected to recover from them or to handle them in any way. Such problems include arithmetic exceptions, such as dividing by zero; pointer exceptions, such as trying to access an object through a null reference; and indexing exceptions, such as attempting to access an array element through an index that is too large or too small. Hence, it seems that it is meaningful to throw a runtime exception when we have an overflow. Below in the same document it is also said: One case where it is common practice to throw a RuntimeException is when the user calls a method incorrectly. For example, a method can check if one of its arguments is incorrectly null. If an argument is null, the method might throw a NullPointerException, which is an unchecked exception. Hence, it also seem that it is meaningful to throw a runtime exception when the PPL is called by passing in an invalid argument. Don't you agree? Cheers, Roberto -- Prof. Roberto Bagnara Computer Science Group Department of Mathematics, University of Parma, Italy http://www.cs.unipr.it/~bagnara/ mailto:bagnara@cs.unipr.it