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null type mismatch with eclipse 4.4rc1 and java 1.8 [message #1378575]

Sat, 24 May 2014 05:38

Eclipse User

using eclipse 4.4RC1 with "compiler compliance level 1.7", the code below is fine, but with "compiler compliance level 1.8", it doesn't work.

if you use "(E)null" instead of "null" the code work with a warning

import org.eclipse.jdt.annotation.Nullable;

public class Test2<E> {

@Nullable
E test() {
return null;
}

void test2() {
E local = null;
}

}

Re: null type mismatch with eclipse 4.4rc1 and java 1.8 [message #1379023 is a reply to message #1378575]

Sat, 24 May 2014 10:11

Eclipse User

That's to be expected! You need to annotate the generic type

> import org.eclipse.jdt.annotation.Nullable;
>
> public class Test2<@Nullable E> {
> @Nullable
> E test() {
> return null;
> }
>
> void test2() {
> E local = null;
> }
> }

I had the same missunderstanding see
https://bugs.eclipse.org/bugs/show_bug.cgi?id=434374#c8 and
https://bugs.eclipse.org/bugs/show_bug.cgi?id=434374#c11

Tom

On 24.05.14 11:38, Nicola Zanaga wrote:
> import org.eclipse.jdt.annotation.Nullable;
>
> public class Test2<E> {
> @Nullable
> E test() {
> return null;
> }
> void test2() {
> E local = null;
> }
> }

Re: null type mismatch with eclipse 4.4rc1 and java 1.8 [message #1379174 is a reply to message #1379023]

Sat, 24 May 2014 11:43

Eclipse User

I have read the bugs, but I don't understand why it is related.
I declared the variable @Nullable, so it has to be nullable, indeed (E)null works ok.

the declaration
public class Test2<@Nullable E> {
}
give me an error, maybe I miss something

However, E type can be null or not null at class level, but I think I always can do a local variable null:

@NonNull E test2() {
E local = null;
...
if( local != null )
return E;
....
}

Thomas Schindl wrote on Sat, 24 May 2014 10:11

That's to be expected! You need to annotate the generic type

> import org.eclipse.jdt.annotation.Nullable;
>
> public class Test2<@Nullable E> {
> @Nullable
> E test() {
> return null;
> }
>
> void test2() {
> E local = null;
> }
> }

I had the same missunderstanding see
https://bugs.eclipse.org/bugs/show_bug.cgi?id=434374#c8 and
https://bugs.eclipse.org/bugs/show_bug.cgi?id=434374#c11

Tom

On 24.05.14 11:38, Nicola Zanaga wrote:
> import org.eclipse.jdt.annotation.Nullable;
>
> public class Test2<E> {
> @Nullable
> E test() {
> return null;
> }
> void test2() {
> E local = null;
> }
> }

Re: null type mismatch with eclipse 4.4rc1 and java 1.8 [message #1379412 is a reply to message #1379174]

Sat, 24 May 2014 14:08

Eclipse User

The semantics of null type annotations in relation to type parameters and type variables still needs to be documented. I hope I'll find the time to include the basic explanations into the Luna migration guide.

Basically, all examples you give work as designed, but:

Quote:

the declaration
public class Test2<@Nullable E> {
}
give me an error, maybe I miss something

this works for me. What error are you seeing?

best,
Stephan

Re: null type mismatch with eclipse 4.4rc1 and java 1.8 [message #1382012 is a reply to message #1379412]

Sun, 25 May 2014 16:52

Eclipse User

i found the problem: i have update eclipse 4.3 to 4.4, my project point to old
org.eclipse.jdt.annotation

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