enums and scope

[richnjones]

Consider these three class definitions in package core


1 package core;
2
3 enum PLANET {
4 MARS
5 }
6
7 public class A {
8 }


1 package core;
2
3 enum PLANET {
4 VENUS
5 }
6
7 public class B {
8 }

1 package core;
2
3 public class A {
4 public static void main(String... s) {
5 PLANET p = PLANET. //here
6 }
7 }


I appear to have created to default access enums called the same thing
but with different values. In which case I believe them to have the
same fully qualified name (core.PLANET) Im not sure how this is
compiling. It is though and my confusion is compounded by the fact
that the PLANET enum used by the //here comment resolves to the enum
in class A. Why does it choose that one?

TIA
Richard

 

[Lew]

Consider these three class definitions in package core


1 package core;
2
3 enum PLANET {
4 MARS
5 }
6
7 public class A {
8 }


1 package core;
2
3 enum PLANET {
4 VENUS
5 }
6
7 public class B {
8 }

1 package core;
2
3 public class A {
4 public static void main(String... s) {
5 PLANET p = PLANET. //here
6 }
7 }


I appear to have created to default access enums called the same thing
but with different values. In which case I believe them to have the
same fully qualified name (core.PLANET) Im not sure how this is
compiling. It is though and my confusion is compounded by the fact
that the PLANET enum used by the //here comment resolves to the enum
in class A. Why does it choose that one?

I don't know how any of it compiles. Your statement labeled "here" isn't even
legal syntax, never mind how it might resolve the "PLANET" reference. (Class
names are supposed to be in mixed case, first letter upper case, CamelCase
throughout, btw.) You shouldn't be able to define two classes A in the same
package, either.

 

[Daniel Dyer]

Consider these three class definitions in package core


1 package core;
2
3 enum PLANET {
4 MARS
5 }
6
7 public class A {
8 }


1 package core;
2
3 enum PLANET {
4 VENUS
5 }
6
7 public class B {
8 }

1 package core;
2
3 public class A {
4 public static void main(String... s) {
5 PLANET p = PLANET. //here
6 }
7 }


I appear to have created to default access enums called the same thing
but with different values. In which case I believe them to have the
same fully qualified name (core.PLANET) Im not sure how this is
compiling. It is though and my confusion is compounded by the fact
that the PLANET enum used by the //here comment resolves to the enum
in class A. Why does it choose that one?

How are you compiling these? I haven't tried it but, if you are compiling
them separately, I would imagine that the second enum's class file would
simply over-write the first enum's class file. If you are compiling them
together I would expect a duplicate definition error. Is your last class
supposed to be called A as well? It's a confusing example.

Dan.

 

[richnjones]

Sorry if the example was confusing. Let me try and explain

1) The seconds A class was a mistake on my part.

2) I know the //here is not valid where it is. I put //here to show
where I seem to get the oddity.


Thanks Daniel for the pointer to do with compiling classes. I think my
compiled classes had got out of sync. When I cleaned and compiled
again I got the compile error I was expecting. My mistake!

Thanks for looking though

Richard

 

[Roedy Green]

I appear to have created to default access enums called the same thing
but with different values. In which case I believe them to have the
same fully qualified name (core.PLANET) Im not sure how this is
compiling. It is though and my confusion is compounded by the fact
that the PLANET enum used by the //here comment resolves to the enum
in class A. Why does it choose that one?

Perhaps the compiler can't tell you have duplicate classes. Whenever
you compile it just replaces the class file with the latest version.
From its point of view, it is not that different from changing the
source file.

To me, the code is just plain nuts and there is no reason to expect it
to work.

You could perhaps find out what is going on by decompiling any class
files that are generated.. See
http://mindprod.com/jgloss/decompiler.html

 

[Roedy Green]

Consider these three class definitions in package core

what happens when you compile this mess all at once with javac *.java?