Design Patterns Java™ Workbook

Chapter 29. Visitor

Figure 29.3. The FindVisitor class effectively adds a find() operation to the

MachineComponent hierarchy.

The visit() methods do not return an object, so the FindVisitor class records the status
of a search in its sought instance variable:

package com.oozinoz.dublin;
import com.oozinoz.machine.;
import java.util.;
public class FindVisitor implements MachineVisitor
{
private MachineComponent sought;
private int soughtId;

public MachineComponent find(
MachineComponent mc, int id)
{
sought = null;
soughtId = id;
mc.accept(this);
return sought;
}