I've tried to browse through the unresolved bugs relating to inner classes
and "protected" access, and I couldn't find one that seemed to describe the
specific problem that I'm running into, so I'm filing it here; my apologies if
this bug is actually a duplicate. Also, I'm guessing that this is a "compiler"
bug and not a "runtime" bug because even though I am getting a failure at run
time, my impression is that it is the compiler's responsibility to generate
the necessary magic to make this sort of inner class access work.

The runtime throws an IllegalAccessError when I try to access a (public) field
in a protected nested class inherited from a superclass in a different package.
Here is a simple example:

// Super.java
package a;
public class Super {
    protected static class Foo {
        public Foo() {} // required because of 4087421??
        public int x;
    }
}

// Sub.java
package b;
public class Sub extends a.Super {
    public static void main(String[] args) {
        Foo f = new Foo();
        f.x = 2; // <== IllegalAccessError thrown here
    }
}

running "java b.Sub" with the JDK1.2Beta3-J promoted build, I get this error:

java.lang.IllegalAccessError: try to access class a/Super$Foo from class b/Sub

I want to do something like this, i.e. have a protected nested class with public
fields, as a mechanism for returning multiple values from a protected method in
the superclass; a container is all that I need, not data abstraction.

Inspecting the bits of the class file a/Super$Foo.class, it is clear that it is
generated as a package access (as opposed to public) top-level class, which
certainly explains why the VM denies the access to the field from the code in
another package. I have vague memories of an early Inner Classes Spec talking
about compiling protected inner classes as *public* top-level classes to take
care of this problem, but apparently that is not being done. Of course, this
issue turns up more often now because of the VM subjecting *all* classes to
access checks.