Java Hashtable linked list

Question

Hi I have the following code for some reason it is throwing a type error: Expected String, Actual Object. Its a hashtable with string keys and linkedlist<string> values.

When iterating through these linkedlist I'm unable to set their values to a string variable. I've used to the getClass() method to ensure it is returning a string class which it is. I'm very confused and any help would be appreciated.

Enumeration t = Scope.keys();
String temp_string;
String temp_string2;
LinkedList temp_linkedlist;
while (t.hasMoreElements())
{
    temp_string = (String)t.nextElement();
    temp_linkedlist = (LinkedList)Scope.get(temp_string);
    for(int num=0; num<temp_linkedlist.size(); num++)
    {
        //Prints out string from linked list  
        System.out.println(temp_linkedlist.get(num).getClass());
        //throws error 
        temp_string2 = temp_linkedlist.get(num);
    }
}

Could you post full statck trace of the error and specify the line in your code in which you have this error? — Sergei Sirik
– Sergei Sirik, Commented Nov 30, 2018 at 1:06
Besides the missing cast, for performance reasons You should not call size() and get(num) on a linked list. It is better to iterate over it. — eckes
– eckes, Commented Nov 30, 2018 at 3:46

Perdi Estaquel · Accepted Answer · 2018-11-30 03:35:17Z

1

When not using generics, all elements in a list are considered Object's to the compiler.

To make your code work, whilst keeping generics out of the equation, try the following:

temp_string2 = (String)temp_linkedlist.get(num);

The reason getClass() gives you a String is because it is evaluated at runtime, not compile time.

answered Nov 30, 2018 at 3:35

Perdi Estaquel

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1 Comment

Alex R Over a year ago

Thanks for your answer, how would i do it with generics?

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