Error codes.

Unlike the standard C and Fortran interfaces, the mpiJava interfaces to MPI calls do not return explicit error codes. The Java exception mechanism will be used to report errors.

• Rationale. The exception mechanism is very widely used by Java libraries. It is inconvenient to use up the single return value of a Java function with an error code. (Java doesn't allow function arguments to be passed by reference, so returning multiple values tends to be more clumsy than in other languages.)(End of rationale.)