//Visitor

//不是很理解这个有问题

import java.util.*;

interface Visitor {

public void visitString(StringElement stringE);

public void visitFloat(FloatElement floatE);

public void visitCollection(Collection collection);

}

//ConcreteVisitor

class ConcreteVisitor implements Visitor {

public void visitCollection(Collection collection) {

// TODO Auto-generated method stub

Iterator iterator = (Iterator)collection.iterator();

while (iterator.hasNext()) {

Object o = iterator.next();

if (o instanceof Visitable) {

((Visitable)o).accept(this);

}

}

}

public void visitFloat(FloatElement floatE) {

System.out.println(floatE.getFe());

}

public void visitString(StringElement stringE) {

System.out.println(stringE.getSe());

}

}

//Element

interface Visitable {

public void accept(Visitor visitor);

}

//ConcreteElement

class FloatElement implements Visitable {

private Float fe;

public FloatElement(Float fe) {

this.fe = fe;

}

public Float getFe() {

return this.fe;

}

public void accept(Visitor visitor) {

visitor.visitFloat(this);

}

}

class StringElement implements Visitable {

private String se;

public StringElement(String se) {

this.se = se;

}

public String getSe() {

return this.se;

}

public void accept(Visitor visitor) {

visitor.visitString(this);

}

}

public class DS23_Visitor{

public static void main(String[] args) {

Visitor visitor = new ConcreteVisitor();

StringElement se = new StringElement("abc");

se.accept(visitor);

FloatElement fe = new FloatElement(new Float(1.5));

fe.accept(visitor);

System.out.println("===========");

List result = new ArrayList();

result.add(new StringElement("abc"));

result.add(new StringElement("abc"));

result.add(new StringElement("abc"));

//result.add(new FloatElement(new Float(1.5)));

// result.add(new FloatElement(new Float(1.5)));

//result.add(new FloatElement(new Float(1.5)));

visitor.visitCollection(result);

}

}