Subclasses implement a piece of code that should be executed in a special way, such as:
asynchronous
within a specified amount of time
after a specified amount of time
Executables are (usually) stateful and should be instantiated for each and every call.
Answers questions like:
does "r|w|x" match {"r","x"} (true).
does "r|w&x" contain {"r","x"} (true).
does "r|w&x" contain {"r"} (true).
does "r|w&x" contain {"x"} (false).
Takes a configured In- and OutputStream such as System.in and System.out
which are used as standard in- and output for an underlying process
such as a command shell.