Re: problem with compiling abstract class with CW (MAC OS X)

• Subject: Re: problem with compiling abstract class with CW (MAC OS X)
• From: Dmitry Markman <email@hidden>
• Date: Mon, 25 Nov 2002 15:41:48 -0500

Dmitry Markman <email@hidden> wrote:

public class AlignCommand extends AbstractCommand {
public static abstract class Alignment {
public final static Alignment LEFTS = new Alignment("Lefts") {
public void moveBy(Figure f, Rectangle anchor) {
Rectangle rr = f.displayBox();
f.moveBy(anchor.x-rr.x, 0);
}
};

private Alignment(String newDescription) {
...
}
public abstract void moveBy(Figure f, Rectangle anchor);
}
}

I think the way to avoid the problem is to not declare Alignment as
abstract, and to define Alignment.moveBy() as an empty method by default,
with an override in each anonymous subclass. Since all the possible
definitions of Alignment's subclasses are entirely under your control in
exactly one source file, I don't see how you're gaining anything by
declaring it abstract.

I'm wondering if CW may be tripping over the combination of a private
constructor, an abstract superclass, and an anonymous inner class. If you
eliminate the 'abstract' qualifier, and CW still won't compile with the
private constructor, then it could be a bug.

I still think it would be worthwhile to run 'javap' on the output of
'javac', to discover what it's doing about the private constructor. I
suspect it's being promoted to the package-visibility, since the compiler
can't really synthesize an accessor-method that replaces a constructor.
Constructors have the special magic name "<init>", and an arbitrary
synthesized name can't be used as a proxy. In that respect, constructors
are different from any other members that the compiler has to deal with in
synthesizing inner-class accesses.

If javac is promoting the private constructor to package-visibility, then
declaring it private isn't gaining you anything. So just having it be
package-visibility in the source would solve the problem.

-- GG
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