Your two lists are the same - they're both of type List so they both get
assigned to the same thing. See below for why.
The solution is to make two classes, one that holds the booleans, and one
that holds the strings. Technically you would only need to do that for one,
but it's probably a good idea to do it for both anyway.
The reason why they're both considered the same: this has to do with how
generics work in Java. It's called type erasure - after the class is
compiled, the generic type is erased, so at runtime it doesn't care what the
type is. Generics are a compile time check.
For example, you could do:
List<String> strings = new ArrayList<String>();
List strings2 = strings;
strings2.add(new Object()); //this line is fine
String string = strings.get(0); //throws ClassCastException
You might think that the strings2.add(new Object()) would have a problem
because strings2 is pointing to strings which is an ArrayList<String>, but
it doesn't because at runtime it doesn't do any checks, or even know that
you put <String> there (well, there's certain ways of figuring it out, but
generally just accept that it doesn't know). All it can do is give a warning
at "List strings2 = strings" because you're doing some potentially type
unsafe things.
On Thu, Jan 6, 2011 at 9:38 AM, Michael Gentry <mgen...@masslight.net>wrote:
> Hi everyone,
>
> Given the following page class:
>
>
> public class Bug
> {
> @Inject
> private Logger log;
>
> @SessionState(create=false)
> private List<Boolean> booleans;
>
> @SessionState(create=false)
> private List<String> strings;
>
> void onActivate()
> {
> log.debug("booleans = " + booleans);
> log.debug("strings = " + strings);
>
> if (booleans == null)
> booleans = new ArrayList<Boolean>();
>
> booleans.add(Boolean.TRUE);
>
> log.debug("booleans: " + booleans);
> log.debug("strings: " + strings);
> log.debug("equal? " + booleans.equals(strings));
> }
> }
>
> I get this output:
>
> DEBUG 2011-01-06 09:35:24,014 booleans = null
> DEBUG 2011-01-06 09:35:24,014 strings = null
> DEBUG 2011-01-06 09:35:24,014 booleans: [true]
> DEBUG 2011-01-06 09:35:24,014 strings: [true]
> DEBUG 2011-01-06 09:35:24,015 equal? true
>
>
> Even though I don't add anything to the strings list or even allocate
> the strings list, it seems to be pointing to the booleans list, which
> is, of course, incorrect. This seems to be happening on both 5.1 and
> 5.2. Am I missing something?
>
> Thanks,
>
> mrg
>
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