Question

I’ve created a hash table and I’m trying to use enumeration in order to print out the keys as well as the values. When I try to compile the code, I keep getting a compile time error saying i need to put a ‘[‘ in new double’s i’ve put into the hashtable.

Before compile:
toys.put(“Race Car”, new double (29.99));

Compile time error says I need to place it like this:

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

what am i doing wrong?

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 only accepts Objects, not primitives, double is a primitive and Double is an Object.
and also consider using generic types for your collections:

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));}