Generics and warning free code

Is it possible to cast to a generic class without compiler warnings?
        Object object = null;
        Comparable comparable1 = (Comparable) object;
        comparable1.compareTo(object); // warning: unchecked call
        Comparable<Object> comparable2 = (Comparable<Object>) object; // warning: unchecked cast
        comparable2.compareTo(object);
        String s = (String) object; // ok
        s.compareTo((String) object); // okMy problem is that casts like these are perfectly useful java code and have nothing to do with interacting with legacy code! Yet it seems no longer possible to write such code without warnings!
Ruud Diterwich
(ps. sorry for the cross post)

No, it is not "legacy code", unless you claim that
any explicit cast is "legacy code". (which would be
an assumption that I strongly disagreed with...)
The compiler feels compelled to issue a warning in
this case solely because Generics are not first-class
Java types and thus not subject to runtime
typechecking at the point of the cast.No, I wouldn't claim all casts are legacy code, and my characterization of the whole example as such was hasty.
I take your point about precisely why the explict cast to (Comparable<Object>) produces a warning. There's no avoiding this without producing a solution that doesn't involve erasure, and I don't think we want to go over that again?
Comparable has been parameterized in 5.0 and as such using it as a raw type and calling compareTo() is now coding in a legacy style that produces warnings. Casting doesn't even need to come into it:
Comparable comparable1 = "";
comparable1.compareTo(null); //warning: [unchecked] unckeched callYou can argue they should have introduced a Comparable2 interface and left the original alone, but that's another tradeoff.

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Edited by: pexatus on Aug 10, 2008 12:48 PM

>
Have a look at AccessController and AccessControlContext. These are the tools you need for this task.
>
By "this task", do you mean, "writing a custom SecurityManager"? Or do you mean the more general task of creating a security policy (such as by writing a policy file) to ensure untrusted code does no damage?
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Similarly, I do not see any methods in AccessControlContext that could tell me whether the current executing code is trusted or not. It, too, has a checkPermission method that will work if I set up the security policy correct, which is what I cannot figure out how to do in the first place, and a getDomainCombiner() method. A DomainCombiner has only a single method, which assumes that I already have an array of ProtectionDomain objects. To create a ProtectionDomain, I need to specify a CodeSource, which is, as the documentation indicates, an extension of "the concept of a codebase". It is at this point I get completely lost in the abstract and generic nouns such as domain, codebase, code source, context, and I do not see how to connect them to concrete nouns that I understand such as class file, package, method, etc. Is it the case that I need to create a CodeSource representing the trusted classes? Is there an elegant way to create a CodeSource representing all the classes in a a project (say, under a given directory, or contained within a given jar file), short of enumerating them or digging into directories and jar files doing a search? And once I create this CodeSource within my program, what do I do with it to specify that I want my security policy to allow all permissions for the classes represented by the CodeSource, and restricted permissions for all classes outside the CodeSource, regardless of call order? (since trusted code will call untrusted code, and I do not want the permissions of the trusted code to be inherited by the untrusted code)
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Dave

Generics and warning free code

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