Intellij Warning - Generic Unchecked Assignment

Question

Possible Duplicate:
Java Generics, how to avoid unchecked assignment warning when using class hierarchy?

Intellij is giving me the warning below. Not sure how to resolve it, or even if I need to resolve it. The warning details says it only applies to JDK 5, and I am using 6. I am wondering if I need to respond to this, and if so, how?

Method call causing warning

List<T> refObject = cache.getCachedRefObject(cacheKey, List.class);

Method being called

public  <T> T getCachedRefObject(String objectKey, Class<T> type) {
    return type.cast(refObjectCache.get(objectKey));
}

Warning details

Unchecked Assignment
JDK 5.0 only. Signals places where an unchecked warning is issued by the compiler, for example:
    void f(HashMap map) {
        map.put("key", "value");
    }

I don't think you can resolve the cast in this case - you can't reify `List` using a `Class` as a type token. — millimoose, Sep 24 '12 at 14:12
@Nambari This has nothing to do with the get-put principle. The cast is unchecked because of the raw type. — millimoose, Sep 24 '12 at 14:15

Peter Lawrey · Answer 1 · 2012-09-24T14:27:10.340

3

Sounds like you have an old version of IntelliJ. This warning really means Java 5.0+ and AFAIK this was changed when IntelliJ supported Java 6 so the warning was there but didn't say "JDK 5.0 only" (it now has support for Java 8)

edited Sep 24 '12 at 14:27

answered Sep 24 '12 at 14:10

Peter Lawrey

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How so? I haven't tried running this through a compiler but it seems he's casting `List` to `List`, there no way to make that not unchecked. – millimoose Sep 24 '12 at 14:11
1

The warning is still there but IntelliJ not longer says "JDK 5.0 only." which may be confusing now. The OP might suspect that in Java 6 this is not a warning. This was used when most people were still on Java 1.4.2 – Peter Lawrey Sep 24 '12 at 14:13
2

Ah, I understood your answer as "upgrading IntelliJ should get rid of the warning". – millimoose Sep 24 '12 at 14:14
@millimoose Good point. Worth clarifying. – Peter Lawrey Sep 24 '12 at 14:27
Thanks. Netbeans is fine with it, but Intellij issues the warning. I have 11.1.3. Looks like it still has the older warning text. Maybe I'll just stick with Netbeans :) – EdgeCase Sep 24 '12 at 17:16
2

Btw still activated in IJ 13. – bric3 Nov 08 '13 at 10:28
I still get the same error on Java 8 and IJ 13. – We are Borg Jun 19 '15 at 15:57

score 2 · Accepted Answer · answered Sep 24 '12 at 14:46

Having played with super type tokens for this, I don't think you can make this type-safe without making extra methods to retrieve collections from your cache and verifying if their contents are of the correct type.

Your options are:

Doing the above, which seems laborious
Suppress the unchecked cast in client code if you know it's correct.
Replace the client code with List<?> refObject = cache.getCachedRefObject(cacheKey, List.class);

The only type-safe variant of these is 3., in that it prevents you from doing operations that the compiler can't prove are type-safe. The obvious downside is that you might want to do some of these operations anyway.

Intellij Warning - Generic Unchecked Assignment

2 Answers2