Java Reference
In-Depth Information
public int getMachineCount()
{
return 1;
}
The
MachineComposite
class also correctly implements
getMachineCount()
,
returning the sum of the counts for each of a composite's components:
public int getMachineCount()
{
int count = 0;
Iterator i = components.iterator();
while (i.hasNext())
{
MachineComponent mc = (MachineComponent) i.next();
count += mc.getMachineCount();
}
return count;
}
These methods are correct so long as
MachineComponent
objects are trees. It can happen,
though, that a composite that you suppose is a tree suddenly becomes not a tree. This is
especially likely to occur when users can edit the composition. Consider an example that
might occur at Oozinoz.
The fireworks engineers at Oozinoz use a GUI application to record and to update
the composition of machinery in the factory. One day, they report a defect regarding the
number of machines that are reported to exist in the factory. You reproduce their object model
with a
plant()
method on an
OozinozFactory
class:
public static MachineComposite plant()
{
MachineComposite plant = new MachineComposite(100);
MachineComposite bay = new MachineComposite(101);
Machine m = new Mixer(102);
Machine n = new Mixer(103);
Machine o = new Mixer(104);
bay.add(m);
bay.add(n);
bay.add(o);
plant.add(m);
plant.add(bay);
return plant;
}
This code produces the
plant
object shown in Figure 5.4.
