java - 使用 “new double”时发生编译时间错误

Question

我已经创建了一个哈希表，并且试图使用枚举来打印键和值。当我尝试编译代码时，我不断收到编译时错误消息，提示我需要在散列表中放入新 double 数的'['。

编译前:
toys.put(“Race Car”，new double(29.99));

编译时错误说我需要这样放置:

toys.put(“Race Car”，new double [29.99]);

我究竟做错了什么？

public static void main(String[] args)  {
  Hashtable toys = new Hashtable();
  Enumeration toyName;
  String getToyName;
  double priceOfToy;
  toys.put("Race Car", new double(29.99));
  toys.put("Toy Bear", new double(15.99));
  toys.put("Action Figure", new double(9.99));
  //Show prices of each toy
  toyName = toys.keys();
  //Uses hasMoreElements method from enumeration to check what is in the hashtable
  while (toyName.hasMoreElements())  {
    //uses nextElement method from enumeration interface to 
    getToyName = (String) toyName.nextElement();
    System.out.println(getToyName +  "is now priced at " + toys.get(getToyName));
  }

}

Answer 1

Map仅接受对象，不接受基元，double是基元，而Double是对象。
并考虑为您的集合使用通用类型:

Hashtable<String, Double> toys = new Hashtable<String, Double>();     
     toys.put("Race Car", new Double(29.99));
      toys.put("Toy Bear", new Double(15.99));
      toys.put("Action Figure", new Double(9.99));}