The following text was written to the standard output stream when the ? program was executed from IntelliJ.
>>> display Bug Pen Dog Cat Bush Computer Circle Phone Book Dowm Snow singer winner lover >>> add help ### invalid operand for add command >>> swap 1 2 >>> display Pen Bug Dog Cat Bush Computer Circle Phone Book Dowm Snow singer winner lover null >>> help HELP - display a menu of commands DISPLAY - display the list of numbers PRINT - print a String (FIRST;LAST;nth) SWAP - exchange two elements (nth;mth) ADD - add a String to the list (FIRST;LAST) EXIT - terminate execution of the program >>> print first Pen >>> print last null >>> add first display >>> display display Pen Bug Dog Cat Bush Computer Circle Phone Book Dowm Snow singer winner lover null >>> exit