禁止由打包库中的父类引起的Java编译器警告

Question

I'm extending a class in a packaged library and the class I'm extending causes an "unchecked" compiler warning. Please note it is not my class that is causing the warning and that is why this is different from other questions I found here in SO.

To comply with code standards in my company, my code must compile without warnings but I can't get rid of this one.

Initially, I wasn't even overriding the offending method. I have overridden it only to add the @SuppressWarnings("unchecked") annotation but that didn't solve the problem.

Within the library, an abstract class ClassA has this method:

public abstract class ClassA {

    protected abstract <T> T methodA(
        String lockName, 
        TransactionCallback<T> txCallback);
}

Also within the library, another class ClassB extends ClassA causing the warning:

public class ClassB extends ClassA {

    @Override
    protected Object methodA(
            String lockName, 
            TransactionCallback txCallback) {
        return someOtherMethod(lockName, txCallback, null);
    }

}

This uses an unchecked operation so, when I try to compile my class:

public class ClassC extends ClassB {

  @SuppressWarnings("unchecked")
  @Override
  protected Object methodA(String lockName, @SuppressWarnings("rawtypes") TransactionCallback txCallback) {
    return super.methodA(lockName, txCallback);
  }

}

I get this warning:

    [javac]   protected Object methodA(String lockName, @SuppressWarnings("rawtypes") TransactionCallback txCallback)
    [javac]                    ^
    [javac]   return type requires unchecked conversion from Object to T
    [javac]   where T is a type-variable:
    [javac]     T extends Object declared in method <T>methodA(String,TransactionCallback<T>)

Is there a way to actually suppress the warning even though I can't recompile the offending class but only its descendant?

Answer 1

I managed to reproduce. @SuppressWarnings at the class-level seems to work, for whatever reason.

@SuppressWarnings("unchecked")
public class ClassC extends ClassB
{
    protected Object methodA(String lockName, TransactionCallback txCallback) {
        return super.methodA(lockName, txCallback);
    }
}