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");
    }

Answer 1

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:

1. Doing the above, which seems laborious
2. Suppress the unchecked cast in client code if you know it’s correct.
3. 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.