Lecture 17
19
abstract class ShellCommand
•Documentation managed here
–helpString and argstring fields (19, 20)
–initialized by protected constructor (31, 32)
•doIt() method (54): 
•abstract public void doIt                      ( StringTokenizer args, Shell sh );
•doIt is passed the rest of the text on the Juno command line, and the Shell it’s acting for
•Each concrete ShellCommand implements its own doIt() - polymorphism
•