设计模式之访问(visitor)

public class VisitorDemo {
	public static void main(String[] args) {
		Collection c = new ArrayList();
		c.add(new StringElement("string1"));
		c.add(new StringElement("string2"));
		c.add(new FloatElement(1.0f));
		c.add(new FloatElement(2.0f));
		Visitor v = new ConcreteVisitor();
		v.visitCollection(c);
	}
}
interface Visitor{
	void visitStringElement(StringElement stringElement);
	void visitFloatElement(FloatElement floatElement);
	void visitCollection(Collection collection);
}
class ConcreteVisitor implements Visitor{
	public void visitCollection(Collection collection) {
		Iterator iter = collection.iterator();
		while(iter.hasNext()){
			Object obj = iter.next();
			if(obj instanceof Visitable){
				((Visitable) obj).accept(this);
			}
		}
	}

	public void visitFloatElement(FloatElement floatElement) {
		System.out.println(floatElement.getValue());
	}

	public void visitStringElement(StringElement stringElement) {
		System.out.println(stringElement.getValue());
	}
	
}

 //http://fengzl.iteye.com/blog/114758