package visitor_pattern;
public abstract class Visitor {
//we actually can use overload directly.
//public abstract void VisitConcreteElement(ConcreteElementA concreteElementA);
//public abstract void VisitConcreteElement(ConcreteElementB concreteElementB);
//even just:public abstract void VisitConcreteElement(Element e);
public abstract void VisitConcreteElementA(ConcreteElementA concreteElementA);
public abstract void VisitConcreteElementB(ConcreteElementB concreteElementB);
}
package visitor_pattern;
public class ConcreteVisitor1 extends Visitor{
public void VisitConcreteElementA(ConcreteElementA concreteElementA) {
System.out.println(this.getClass().getName()+" visit "+concreteElementA.getClass().getName());
}
public void VisitConcreteElementB(ConcreteElementB concreteElementB){
System.out.println(this.getClass().getName()+" visit "+concreteElementB.getClass().getName());
}
}
package visitor_pattern;
public class ConcreteVisitor2 extends Visitor{
public void VisitConcreteElementA(ConcreteElementA concreteElementA) {
System.out.println(this.getClass().getName()+" visit "+concreteElementA.getClass().getName());
}
public void VisitConcreteElementB(ConcreteElementB concreteElementB){
System.out.println(this.getClass().getName()+" visit "+concreteElementB.getClass().getName());
}
}
package visitor_pattern;
public abstract class Element{
public abstract void accept(Visitor v);
}
package visitor_pattern;
public class ConcreteElementA extends Element{
@Override
public void accept(Visitor v) {
v.VisitConcreteElementA(this);
}
public void operationA() {
}
}
package visitor_pattern;
public class ConcreteElementB extends Element{
@Override
public void accept(Visitor v) {
v.VisitConcreteElementB(this);
}
public void operationB() {
}
}
package visitor_pattern;
import java.util.ArrayList;
public class ObjectStructure {
private ArrayList<Element>elements = new ArrayList<Element>();
public void attach(Element e) {
elements.add(e);
}
public void detach(Element e) {
elements.remove(e);
}
public void accept(Visitor v) {
for(Element e:elements) {
e.accept(v);
}
}
}
package visitor_pattern;
public class Main {
public static void main(String args[]) {
ObjectStructure o = new ObjectStructure();
o.attach(new ConcreteElementA());
o.attach(new ConcreteElementB());
ConcreteVisitor1 v1 = new ConcreteVisitor1();
ConcreteVisitor2 v2 = new ConcreteVisitor2();
o.accept(v1);
o.accept(v2);
}
}
This is a general introduction to the 23 design patterns：
https://blog.csdn.net/GZHarryAnonymous/article/details/81567214