Warnings “unchecked call” and “unchecked conversion”

Question

When I compile my code I get 4 warnings - but how do I make them disappear? (and I don't mean with @SuppressWarnings)

PS: Obviously this must have been asked before - but either I cannot find it or I cannot apply it.

---

Output

warning: [unchecked] unchecked call to BaseWorker(C) as a member of the raw type BaseWorker
[warn] return new BaseWorker(this);

warning: [unchecked] unchecked conversion
[warn] found   : com.crashnote.BaseWorker
[warn] required: com.crashnote.BaseWorker<C>
[warn] return new BaseWorker(this);

warning: [unchecked] unchecked call to SubWorker(C) as a member of the raw type SubWorker
[warn] return new SubWorker(this);

warning: [unchecked] unchecked conversion
[warn] found   : com.crashnote.SubWorker
[warn] required: com.crashnote.SubWorker<C>
[warn] return new SubWorker(this);

---

Source Code

BaseConfig : instantiates BaseWorker

public class BaseConfig<C extends BaseConfig> {

    public BaseConfig(final Object c) {
    }

    public BaseWorker<C> getWorker() {
        return new BaseWorker(this);
    }
}

BaseWorker

public class BaseWorker<C extends BaseConfig> {

    public BaseWorker(final C config) {
    }
}

SubConfig : instantiates SubWorker

class SubConfig<C extends SubConfig> extends BaseConfig<C> {

    public SubConfig(final Object c) {
        super(c);
    }

    @Override
    public SubWorker<C> getWorker() {
        return new SubWorker(this);
    }
}

SubWorker : inherits from SubWorker

public class SubWorker<C extends BaseConfig> extends BaseWorker<C> {

      public SubWorker(final C config) {
          super(config);
      }  
}

---

Edit

I tried the provided solutions but for some reason it fails now.

A)

return new BaseWorker<BaseConfig>(this);

results in

incompatible types
[error] found   : BaseWorker<BaseConfig>
[error] required: BaseWorker<C>
[error] return new BaseWorker<BaseConfig>(this);

B)

return new BaseWorker<C>(this);

results in

cannot find symbol
[error] symbol  : constructor BaseWorker(BaseConfig<C>)
[error] location: class BaseWorker<C>
[error] return new BaseWorker<C>(this);

Hm, maybe I'm doing something wrong. This is Java 6 by the way, in case it matters.

Answer 1

Instead of returning plain

return new BaseWorker(this);

Make it generic, because your BaseWorker class is defined as generic.

return new BaseWorker<C>(this);

Same rule applies for SubWorker also.

return new SubWorker<C>(this);

Update:

Based on exception message, your constructor also missing generics.

Answer 2

Try

 return new BaseWorker<C>(this);

and

 return new SubWorker<C>(this);

Answer 3

Well, after applying the answers to my code I found out that they are actually wrong. Here is what seems to work.

BaseConfig now has a print() method (just to check we have the right type later) and adds a generic to the instantiation of BaseWorker .

public class BaseConfig<C extends BaseConfig> {

    public BaseConfig(final Object c) {
    }

    public BaseWorker<C> getWorker() {
        return new BaseWorker<C>(this);
    }

    public void print() {
        //
    }
}

Now this is where it gets interesting, BaseWorker has a constructor with a generic. This seems totally redundant - but it was the only way I found that worked. When you write just <C> it appears to be a new "local" generic additionally to the one of the class and a compiler error is raised ( cannot find symbol: method print() ).

public class BaseWorker<C extends BaseConfig> {

    public <C extends BaseConfig> BaseWorker(final C config) {
        config.print();
    }
}

SubConfig and SubWorker are changed accordingly.

PS: If this is utter nonsense please tell me :)