interface Visitor { 
  void visit(Gladiolus g); 
 
  void visit(Chrysanthemum c); 
} 

// concrete visitor   名稱訪問(wèn) 
class StringVisitor implements Visitor { 
  String s; 
 
  public String toString() { 
    return s; 
  } 
 
  public void visit(Gladiolus g) { 
    s = "Gladiolus"; 
  } 
 
  public void visit(Chrysanthemum c) { 
    s = "Chrysanthemum"; 
  } 
} 

// concrete visitor   蜜蜂訪問(wèn) 
class BeeVisitor implements Visitor { 
  public void visit(Gladiolus g) { 
    System.out.println("蜜蜂 來(lái) 訪問(wèn) Gladiolus"); 
  } 
 
  public void visit(Chrysanthemum c) { 
    System.out.println("蜜蜂 來(lái) 訪問(wèn) Chrysanthemum"); 
  } 
} 
 

interface Flower { 
  void accept(Visitor v); 
} 

/* 
 * concrete element   菊花 
 */ 
class Chrysanthemum implements Flower { 
  public void accept(Visitor v) { 
    v.visit(this); 
  } 
} 

// concrete element   劍蘭 
class Gladiolus implements Flower { 
  public void accept(Visitor v) { 
    v.visit(this); 
  } 
} 

//這是Flower一個(gè)對(duì)象生成器 
class FlowerGenerator { 
  private static Random rand = new Random(); 
 
  public static Flower newFlower() { 
    switch (rand.nextInt(2)) { 
    default: 
    case 0: 
      return new Gladiolus(); 
    case 1: 
      return new Chrysanthemum(); 
    } 
  } 
} 

public class Test { 
  /* 
   * 首先在客戶端先獲得一個(gè)具體的訪問(wèn)者角色 遍歷對(duì)象結(jié)構(gòu) 對(duì)每一個(gè)元素調(diào)用accept方法，將具體訪問(wèn)者角色傳入 這樣就完成了整個(gè)過(guò)程 
   */ 
  public static void main(String args[]) { 
    List<Flower> flowers = new ArrayList<Flower>(); 
    for (int i = 0; i < 10; i++) 
      flowers.add(FlowerGenerator.newFlower()); 
    Visitor visitor = new StringVisitor(); 
    Iterator<Flower> iterator = flowers.iterator(); 
    while (iterator.hasNext()) { 
      iterator.next().accept(visitor); 
      System.out.println(visitor); 
    } 
    System.out.println("---------------"); 
    /* 
     * 一個(gè)新的訪問(wèn)行為 ：BeeVisitor 蜜蜂訪問(wèn) 
     */ 
    Visitor visitor2 = new BeeVisitor(); 
    for (Flower flower : flowers) { 
      flower.accept(visitor2); 
    } 
 
  } 
} 

Gladiolus 
Chrysanthemum 
Chrysanthemum 
Gladiolus 
Chrysanthemum 
Chrysanthemum 
Chrysanthemum 
Chrysanthemum 
Gladiolus 
Gladiolus 
--------------- 
蜜蜂 來(lái) 訪問(wèn) Gladiolus 
蜜蜂 來(lái) 訪問(wèn) Chrysanthemum 
蜜蜂 來(lái) 訪問(wèn) Chrysanthemum 
蜜蜂 來(lái) 訪問(wèn) Gladiolus 
蜜蜂 來(lái) 訪問(wèn) Chrysanthemum 
蜜蜂 來(lái) 訪問(wèn) Chrysanthemum 
蜜蜂 來(lái) 訪問(wèn) Chrysanthemum 
蜜蜂 來(lái) 訪問(wèn) Chrysanthemum 
蜜蜂 來(lái) 訪問(wèn) Gladiolus 
蜜蜂 來(lái) 訪問(wèn) Gladiolus