设计模式之访问者模式
// 元素接口
interface Element {
void accept(Visitor visitor);
}
// 具体元素
class ConcreteElementA implements Element {
@Override
public void accept(Visitor visitor) {
visitor.visit(this);
}
}
class ConcreteElementB implements Element {
@Override
public void accept(Visitor visitor) {
visitor.visit(this);
}
}
// 访问者接口
interface Visitor {
void visit(ConcreteElementA element);
void visit(ConcreteElementB element);
}
// 具体访问者
class ConcreteVisitor implements Visitor {
@Override
public void visit(ConcreteElementA element) {
System.out.println("ConcreteElementA is visited.");
}
@Override
public void visit(ConcreteElementB element) {
System.out.println("ConcreteElementB is visited.");
}
}
// 对象结构（这里简化为一个简单的数组）
class ObjectStructure {
private List<Element> elements = new ArrayList<>();
public void attach(Element element) {
elements.add(element);
}
public void accept(Visitor visitor) {
for (Element element : elements) {
element.accept(visitor);
}
}
}
// 示例
public class VisitorPatternDemo {
public static void main(String[] args) {
ObjectStructure objectStructure = new ObjectStructure();
objectStructure.attach(new ConcreteElementA());
objectStructure.attach(new ConcreteElementB());
Visitor visitor = new ConcreteVisitor();
objectStructure.accept(visitor);
}
}