Class Diautil offers methods that make it easy to calculate execution time by means of a timer; further it offers a method that shows the name of the user and can be called right before program termination in order to indicate the user's name and the program's running time.
Class Esdia offers methods that make it easy to read numeric and alphanumeric values from the keyboard while showing a prompt; errors are signalled and indeed it is possible to read only non-empty strings.
Class OpMat offers a list of static methods that deal with atomic and String arrays; their purpose is to read from the keyboard, print to screen, import from disk (CSV and columnar), export to disk (CSV and columnar), serialize (save) to disk, read from disk, sum, multiply and join (only String arrays).
Class OpVect offers a list of static methods that deal with numeric vectors; it allows the user to read vectors from the keyboard, and to calculate the dot, cross and mixed product, as well as the modulus of a vector and the distance between two points.
Class RandomDate generates random a random LocalDate between two given ones; methods are not static hence an instance of RandomDate must be created before using the one method in this class, nextDate().