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ArrayList

suavedeep kaur
Ranch Hand

Joined: Jun 02, 2008
Posts: 36
i am trying to create an ArrayList and then display it using an Array but theres an exception at runtime



please explain me whats the problem ???
[Dave - formatted and added code tags]
[ July 26, 2008: Message edited by: David O'Meara ]


Suavedeep kaur
SCJP
Agarwal Priyanka
Greenhorn

Joined: Jul 25, 2008
Posts: 20
the better way to examine any exception is using the try-catch block. you must try that to find the exception first.


keep trying...thats the way to success...<br />with best regards...<br />p.agarwal
David O'Meara
Rancher

Joined: Mar 06, 2001
Posts: 13459

Providing the exceprion that gets thrown would also be helpful.
Rob Spoor
Sheriff

Joined: Oct 27, 2005
Posts: 19723
    
  20

Here's the output:

Now this makes sense. Your ArrayList contains Strings. Then, when using the toArray method, you try to put all those elements into an Integer[]. Of course Integer[] cannot store String, that's where the ArrayStoreException comes from. As specified in the Javadoc of java.util.Collection:


Change Integer[] to String[] and it will work.


Mind you, I do think this is a mistake in the API. The method signature is "<T> T[] toArray(T[] a)" - it should have been "<T super E> T[] toArray(T[] a)" to enforce that T is E or a superclass of E (or an interface that is implemented by E). In your example, with E being String, that would limit T to one of the following:
- String
- Object
- Serializable
- CharSequence
- Comparable<String>
[ July 26, 2008: Message edited by: Rob Prime ]

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suavedeep kaur
Ranch Hand

Joined: Jun 02, 2008
Posts: 36
thanks alot for the help Rob
 
I agree. Here's the link: http://aspose.com/file-tools
 
subject: ArrayList