jshell> /open Shape.java

jshell> /open Rectangle.java

jshell> Object o = new Rectangle(3,4);
o ==> Rectangle(3.0, 4.0)

jshell> o.toString()
$4 ==> "Rectangle(3.0, 4.0)"

jshell> //Delegation:  Method calls are delegated to the

jshell> //object.

jshell> /exit
|  Goodbye