Cleanin up Java unchecked conversions

[tmiranda]

I'm in the process of cleaning up some Java code and can't figure out how to eliminate an "unchecked conversion" warning I'm getting. Here is the code:

        // Get the RSSItems in a LinkedList.
        LinkedList<RSSItem> ChanItems = new LinkedList<RSSItem>();
        ChanItems = rsschan.getItems();

The problem is that rsschan.getItems() returns a LinkedList and not specifically a LinkedList<RSSItem>. (I'm assuming that's because getItems() was not written using generics.)

I'd like to avoid using @SuppressWarnings because that might hide warnings I really need to see.

What is the best way to accomplish this?

[stuckless]

Originally Posted by tmiranda

I'm in the process of cleaning up some Java code and can't figure out how to eliminate an "unchecked conversion" warning I'm getting. Here is the code:

        // Get the RSSItems in a LinkedList.
        LinkedList<RSSItem> ChanItems = new LinkedList<RSSItem>();
        ChanItems = rsschan.getItems();

The problem is that rsschan.getItems() returns a LinkedList and not specifically a LinkedList<RSSItem>. (I'm assuming that's because getItems() was not written using generics.)

I'd like to avoid using @SuppressWarnings because that might hide warnings I really need to see.

What is the best way to accomplish this?

I guess there are a couple of options...

Adding @SuppressWarnings("unchecked") just above the statement...

        // Get the RSSItems in a LinkedList.
        @SuppressWarnings("unchecked")
        LinkedList<RSSItem> ChanItems = new LinkedList<RSSItem>();
        ChanItems = rsschan.getItems();

You other option is to use a very generic list...

        // Get the RSSItems in a LinkedList.
        LinkedList<?> ChanItems = new LinkedList<RSSItem>();
        ChanItems = rsschan.getItems();

[broconne]

Originally Posted by tmiranda

I'm in the process of cleaning up some Java code and can't figure out how to eliminate an "unchecked conversion" warning I'm getting. Here is the code:

        // Get the RSSItems in a LinkedList.
        LinkedList<RSSItem> ChanItems = new LinkedList<RSSItem>();
        ChanItems = rsschan.getItems();

The problem is that rsschan.getItems() returns a LinkedList and not specifically a LinkedList<RSSItem>. (I'm assuming that's because getItems() was not written using generics.)

I'd like to avoid using @SuppressWarnings because that might hide warnings I really need to see.

What is the best way to accomplish this?

Tmiranda,
You have a few options. Although, first looking at the code - the call to "new LinkedList<RSSItem>()" is unnecessary. In your second step you are setting the ChanItems to the value returned by rssChan.getItems(); So effectively that code could become

LinkedList<RSSItem> ChanItems = rsschan.getItems();

On a minor side note, Java conventions dictate variable names are lowerCamelCase so if you care, the standard convention would be:

LinkedList<RSSItem> chanItems = rssChan.getItems();

But if you are the only one looking at your code - then it really doesn't matter

For the unchecked warning question. You are getting the error for a good reason, as you speculated you are asking the compiler to guarantee that only Objects of type RSSItem will be in the list named chanItems, however the method you are calling to retrieve that list doesn't use generics and therefore does not guarentee (via generics - it may via its javadoc) that the LinkedList will only have objects of type RSSItem.

(1) If you know that rssChan.getItems(); will always return a LinkedList that contains only RSSItems and you want your program throw a ClassCastException in the case where it does not, there is nothing wrong with using @SuppressWarnings("unchecked") at the site of the call - that will not hide other errors as long as you scope it just to the variable declaration:

@SuppressWarnings("unchecked")
LinkedList<RSSItem> chanItems = rssChan.getItems();

(2) Cast every object yourself, checking the type with instance of - this guarantees only objects of type RSSItem can get in the list and you can log items in the returned list that weren't of the expected type.

List<RSSItem> chanItems = new LinkedList<RSSItem>();
for(Object object : rssChan.getItems()){
  if(object instanceof RSSItem){
     RSSItem rssItem = (RSSItem) object;
     chanItems.add(rssItem);
  }
  else{
     Log("OMG Ponies!  Unexpected object type in return list");
  }
}

I didn't compile the above code, so not 100% sure it is accurate, but it should be in spirit.

[tmiranda]

Thanks to both. I didn't realize I could use @SuppressWarnings() at the individual statement level so I think I'll just use that.

I know the new LinkList<> is not necessary, I was juts doing some testing