Design Patterns Java™ Workbook

Interpreter (Chapter 25)

SOLUTION 25.1

The following program will shut down all the machines that MachineLine controls, except for the unload buffer: package com.oozinoz.robot.interpreter; import com.oozinoz.machine.*; public class ShowIf { public static void main(String[] args) { Context c = MachineLine.createContext(); Variable m = new Variable("m"); Constant ub = new Constant(c.lookup("UnloadBuffer1501")); Term t = new Equals(m, ub); IfCommand ic = new IfCommand( t, new NullCommand(), new ShutdownCommand(m)); ForMachines fc = new ForMachines(m, ic); fc.execute(c); } } The fc object is an interpreter; it interprets execute() to mean shut down all machines except the unload buffer.

SOLUTION 25.2

One solution is: package com.oozinoz.robot.interpreter; ...