Java设计模式之访问者模式使用场景及代码示例

public interface IVisitor {
 public void accept(Feman feman);
 
 public void accept(Man man);
}

public class Visitor implements IVisitor {
 public void accept(Feman feman) {
  System.out.println(feman.getSex() + ":执行相关操作");
 }
 
 public void accept(Man man) {
  System.out.println(man.getSex() + ":执行相关操作");
 }
}

public abstract class Person {
 private String sex;
 public String getSex() {
  return sex;
 }
 public void setSex(String sex) {
  this.sex = sex;
 }
 public void accept(Visitor visitor) {
 };
}

public class Man extends Person {
 public Man() {
  this.setSex("男");
 }
 
 @Override
 public void accept(Visitor visitor) {
  visitor.accept(this);
 }
}

public class Feman extends Person {
 public Feman() {
  this.setSex("女");
 }
  
 @Override
 public void accept(Visitor visitor){
  visitor.accept(this);
 }
}

public class ObjectStruture {
 public static List<person> getList() {
  List<person> list = new ArrayList<person>();
  list.add(new Man());
  list.add(new Feman());
  list.add(new Feman());
  return list;
 }
}

Visitor visitor = new Visitor();
List<person> list = ObjectStruture.getList();
for (Person e : list) {
 e.accept(visitor);
}

男:执行相关操作
女:执行相关操作
女:执行相关操作

public interface Visitor
{
	public void visit(GladiolusConcreteElement gladiolus);
	public void visit(ChrysanthemumConreteElement chrysanthemum);
}
public interface FlowerElement
{
	public void accept(Visitor visitor);
}
public class GladiolusConcreteElement implements FlowerElement
{
	@Override
	 public void accept(final Visitor visitor)
	 {
		visitor.visit(this);
	}
}
public class ChrysanthemumConreteElement implements FlowerElement
{
	@Override
	 public void accept(final Visitor visitor)
	 {
		visitor.visit(this);
	}
}
public class GladiolusVisitor implements Visitor
{
	@Override
	 public void visit(final GladiolusConcreteElement gladiolus)
	 {
		System.out.println(this.getClass().getSimpleName() + " access " + gladiolus.getClass().getSimpleName());
	}
	@Override
	 public void visit(final ChrysanthemumConreteElement chrysanthemum)
	 {
		System.out.println(this.getClass().getSimpleName() + " access " + chrysanthemum.getClass().getSimpleName());
	}
}
public class ChrysanthemumConreteElement implements FlowerElement
{
	@Override
	 public void accept(final Visitor visitor)
	 {
		visitor.visit(this);
	}
}
public class ObjectStructure
{
	private final List<FlowerElement> elements = new ArrayList<FlowerElement>();
	public void addElement(final FlowerElement e)
	 {
		elements.add(e);
	}
	public void removeElement(final FlowerElement e)
	 {
		elements.remove(e);
	}
	public void accept(final Visitor visitor)
	 {
		for (final FlowerElement e : elements)
		  {
			e.accept(visitor);
		}
	}
}
public class Client
{
	public static void main(final String[] args)
	 {
		final ObjectStructure os = new ObjectStructure();
		os.addElement(new GladiolusConcreteElement());
		os.addElement(new ChrysanthemumConreteElement());
		final GladiolusVisitor gVisitor = new GladiolusVisitor();
		final ChrysanthemumVisitor chVisitor = new ChrysanthemumVisitor();
		os.accept(gVisitor);
		os.accept(chVisitor);
	}
}

GladiolusVisitor access GladiolusConcreteElement
GladiolusVisitor access ChrysanthemumConreteElement
ChrysanthemumVisitor access GladiolusConcreteElement
ChrysanthemumVisitor access ChrysanthemumConreteElement