ClassCast Exception while casting to type String

Question

Dear Java users
While coding a parse routine in a session EJB , I created a vector and added some elements to it.
Naturally these elements are of type object.
Now, while extracting elements out of the vector I tried to cast them to the actual type that the elements are.
Most of the elements are of type String and some of type Long and Double.Note that these are all Object wrappers not primitives.
The code compiles fine, however at run time I get the following error:
java.lang.ClassCastException : java.lang.String
I tried to do the casting two ways: (String) object and object.toString(). In both cases I got the same error.
Here is a snippet of my code where I get the error:
RETAIL_TRANX retail_db = retail_home.create(columns.elementAt(0).toString(),
columns.elementAt(1).toString(),................
Any ideas on why this is happening and how best should I cast to String.
Thank you for any help you can provide
Best
Naveen

Answer 1

RETAIL_TRANX retail_db = retail_home.create(columns.elementAt(0).toString(),
columns.elementAt(1).toString(),................
I'd say that the code above calls the toString() implemented in the Object class because that's what elementAt() returns. If you want String objects as arguments to the create method, you want the toString() implemented in the subclasses String, Long, and Double. To achieve this, try the following:
RETAIL_TRANX retail_db = retail_home.create(((String)columns.elementAt(0)).toString()...
This code casts the Object class object returned by elementAt to a String first and then it calls the toString() method on the String object resulting from the cast. The toString() that executes should be the one in the String rather than Object class.
This is going to fail if elementAt() doesn't return an object that can be cast to a String. In this case, what you might want to do first is test the type of object returned with the instanceof operator. Then cast to the appropriate type, in each case calling toString() after the cast has been made.
Regards,
Steve