汉诺塔的java实现

汉诺塔问题描述：
    假设有三个命名为X（TOWER 1),Y(TOWER 2),Z(TOWER 3)的塔座，在塔座X上有n个直径大小各不相同，依次从小到大编号为1,2,3,...,n的圆盘。现要求将X塔座上的n个圆盘移到Z塔座上并按同样顺序叠排，
圆盘移动时必须遵循下列规则：
1）每次只能移动一个圆盘；
2）圆盘可以插在X,Y,Z中的任意塔座上；
3）任何时刻都不能将一个较大的圆盘压在较小的圆盘之上。

public class Hanoi{
 
    //塔
    class Tower<E> {
       //塔编号
       private int number;
       //塔名称
       private String name;
       //存放盘子的栈
       private Stack<E> stack = new Stack<E>();
       
       public Tower(int number,String name) {
           this.number = number;
           this.name = name;
       }
              
       public int getNumber() {
           return number;
       }
 
       public String getName() {
           return name;
       }
 
       public Stack<E> getStack() {
           return stack;
       }
       
    }
    
    //盘子
    class Tray {
       //盘子编号
       private int number;
       //盘子名称
       private String name;
       
       public Tray(int number,String name) {
           this.number = number;
           this.name = name;
       }
       
       public int getNumber() {
           return number;
       }
       
       public String getName() {
           return name;
       }
       
       public String toString() {
           return name;
       }
    }
    
    public <T> void hanoi(int num,Tower<T> from,Tower<T> middle,
           Tower<T> to) {
       if(num == 1) {
           move(from,middle,to);
       } else {
           //将num-1个盘子从from塔上移到middle塔上
           hanoi(num-1,from,to,middle);
           //将第num个盘子移到to塔上
           move(from,middle,to);
           //将num-1个盘子从middle塔上移到to塔上
           hanoi(num-1,middle,from,to);
       }
    }
    
    private <E> void move(Tower<E> from,Tower<E> middle ,Tower<E> to) {
       E tray = from.getStack().pop();
       to.getStack().push(tray);
       StringBuilder sb = new StringBuilder();
       sb.append("=====================Hanoi.move()======================\n")
       .append(" Move tray : ").append(((Tray)tray).getName())
       .append(" from ").append(from.getName()).append(" to ")
       .append(to.getName()).append("\n ")
       .append(from.getName()).append(":").append(format(from)).append(",")
       .append(middle.getName()).append(":").append(format(middle)).append(",")
       .append(to.getName()).append(":").append(format(to));
       System.out.println(sb.toString());
    }
  
    private <E> String format(Tower<E> tower) {
       Iterator<E> i = tower.getStack().iterator();
       if (! i.hasNext())
           return "[]";
       StringBuilder sb = new StringBuilder();
       sb.append('[');
       while(i.hasNext()) {
           sb.append(i.next().toString()).append(",");
       }
       sb.replace(sb.length()-1, sb.length(), "]");
       return sb.toString();
    }

    public static void main(String[] args) {
       Hanoi hanoi = new Hanoi();
       Tower<Tray> from = hanoi.new Tower<Tray>(1, "1号塔");
       Tower<Tray> middle = hanoi.new Tower<Tray>(2, "2号塔");
       Tower<Tray> to = hanoi.new Tower<Tray>(3, "3号塔");
       int num = 4;
       for (int i = num; i >0; i--) {
           Tray tray = hanoi.new Tray(i,i+"号盘子");
           from.getStack().push(tray);
       }
       hanoi.hanoi(num, from, middle, to);
    } 
}