Java Reference
In-Depth Information
Figure 25.4. The
Term
hierarchy includes classes that are effectively Booleans.
The
Equals
class and the
HasMoreMaterial
class return
null
to indicate false. You can
create, for example, an
Equals
term that compares a variable to the constant value of
the unload buffer:
Constant ub = new Constant(c.lookup("UnloadBuffer1501"));
Term t = new Equals(m, ub);
You can use an instance of
Equals
as the conditional term in an
IfCommand
object.
An
IfCommand
object has a term, a
body
command, and an
elseBody
command. When it
executes, an
IfCommand
object executes its main
body
command unless its term evaluates
to
null
, in which case it executes its
elseBody
command:
package com.oozinoz.robot.interpreter;
import com.oozinoz.machine.*;
public class IfCommand extends Command
{
protected Term term;
protected Command body;
protected Command elseBody;
