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[foo.bar.Frame] can not inherit from [java.awt.Frame]

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  [foo.bar.Frame] can not inherit from [java.awt.Frame] Maciej Labanowicz <m.labanowicz@gmail.com> - 2012-04-11 04:56 -0700
    Re: can not inherit from [java.awt.Frame] Paul Cager <paul.cager@googlemail.com> - 2012-04-11 05:51 -0700
      Re: can not inherit from [java.awt.Frame] Lew <noone@lewscanon.com> - 2012-04-11 08:13 -0700
        Re: can not inherit from [java.awt.Frame] Paul Cager <paul.cager@googlemail.com> - 2012-04-11 09:37 -0700
    Re: [foo.bar.Frame] can not inherit from [java.awt.Frame] Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2012-04-11 12:59 +0000
    Re: [foo.bar.Frame] can not inherit from [java.awt.Frame] markspace <-@.> - 2012-04-11 08:24 -0700
      Re: [foo.bar.Frame] can not inherit from [java.awt.Frame] Patricia Shanahan <pats@acm.org> - 2012-04-11 09:34 -0700
        Re: [foo.bar.Frame] can not inherit from [java.awt.Frame] markspace <-@.> - 2012-04-11 10:01 -0700
    Re: [foo.bar.Frame] can not inherit from [java.awt.Frame] Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-04-11 11:18 -0700
      Re: [foo.bar.Frame] can not inherit from [java.awt.Frame] Lew <lewbloch@gmail.com> - 2012-04-11 12:18 -0700

#13469 — [foo.bar.Frame] can not inherit from [java.awt.Frame]

Hi,

I'm trying to compile simple class, named Frame in package foo.bar:

--[beg]--[Frame.java]-----------------------------------
package foo.bar;
import  java.awt.Frame;
public class Frame extends java.awt.Frame {
  public static final long serialVersionUID = 1L;
  public static void main(String [] args) {
    System.out.println("HELLO: args = " + args);
  }
}
--[eof]--[Frame.java]-----------------------------------

/> javac Frame.java
Frame.java:2: error: foo.bar.Frame is already defined in this
compilation unit
import  java.awt.Frame;
^
1 error

I have also tried with:
- public class Frame extends java.awt.Frame {
+ public class foo.bar.Frame extends java.awt.Frame {

But the error is:
Frame.java:3: error: '{' expected
public class foo.bar.Frame extends java.awt.Frame {
                ^
1 error

Is there any possibility to create such class in java ?

Regards

--
Maciek

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#13471 — Re: can not inherit from [java.awt.Frame]

On Apr 11, 12:56 pm, Maciej Labanowicz <m.labanow...@gmail.com> wrote:
> /> javac Frame.java
> Frame.java:2: error: foo.bar.Frame is already defined in this
> compilation unit
> import  java.awt.Frame;
> ^
> 1 error

That should work. Are you sure you have shown us the whole file?

One problem that would lead to these symptoms is if you had
accidentally duplicated the class declaration in the file, such as
(untested):

  package foo;

  public class Frame {
    // Lots of stuff
  }

  public class Frame {
    // Lots of stuff
  }

If that's not the case, which compiler are you using?

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#13480 — Re: can not inherit from [java.awt.Frame]

On 04/11/2012 05:51 AM, Paul Cager wrote:
> On Apr 11, 12:56 pm, Maciej Labanowicz<m.labanow...@gmail.com>  wrote:
>> />  javac Frame.java
>> Frame.java:2: error: foo.bar.Frame is already defined in this
>> compilation unit
>> import  java.awt.Frame;
>> ^
>> 1 error
>
> That should work. Are you sure you have shown us the whole file?

No, it shouldn't work.

> One problem that would lead to these symptoms is if you had
> accidentally duplicated the class declaration in the file, such as
> (untested):
>
>    package foo;
>
>    public class Frame {
>      // Lots of stuff
>    }
>
>    public class Frame {
>      // Lots of stuff
>    }
>
> If that's not the case, which compiler are you using?

He's using a standards-conforming compiler, which is all that matters in this 
case.

-- 
Lew
Honi soit qui mal y pense.
http://upload.wikimedia.org/wikipedia/commons/c/cf/Friz.jpg

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#13485 — Re: can not inherit from [java.awt.Frame]

On Apr 11, 4:13 pm, Lew <no...@lewscanon.com> wrote:
> On 04/11/2012 05:51 AM, Paul Cager wrote:

> > That should work. Are you sure you have shown us the whole file?
>
> No, it shouldn't work.

Ah yes, you're right. I hadn't seen that import.

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#13473

Maciej Labanowicz <m.labanowicz@gmail.com> wrote:
> I'm trying to compile simple class, named Frame in package foo.bar:
> --[beg]--[Frame.java]-----------------------------------
> package foo.bar;
> import  java.awt.Frame;

This import statement tells the Java compiler, that when it 
encounters a bare Frame literal, that it should consider that
from java.awt.Frame.  This obviously cannot work, if you have
a different class Frame (foo.bar.Frame) already.

Solution 1 would be to call your class differently, like MyFrame

Solution 2 would be to remove the "import" statement for java.awt.Frame.
After doing so, ...
> - public class Frame extends java.awt.Frame {
this one ought to work.

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#13481

On 4/11/2012 4:56 AM, Maciej Labanowicz wrote:

> Frame.java:2: error: foo.bar.Frame is already defined in this
> compilation unit


I *think* what the compiler is saying using Frame as an unqualified name 
collides with the existing foo.bar.Frame usage.

The solution is just to not use the "import" statement.

package quicktest;

class Frame extends java.awt.Frame {
   public static final long serialVersionUID = 1L;
   public static void main(String [] args) {
     System.out.println("HELLO: args = " + args);
   }
}

If your compiler can find "import java.awt.Frame", then it can find 
java.awt.Frame without the import.  You don't need import, it just 
allows you to shorten the FQN to just the class name.

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#13484

On 4/11/2012 8:24 AM, markspace wrote:
> On 4/11/2012 4:56 AM, Maciej Labanowicz wrote:
>
>> Frame.java:2: error: foo.bar.Frame is already defined in this
>> compilation unit
>
>
> I *think* what the compiler is saying using Frame as an unqualified name
> collides with the existing foo.bar.Frame usage.
>
> The solution is just to not use the "import" statement.
>
> package quicktest;
>
> class Frame extends java.awt.Frame {
> public static final long serialVersionUID = 1L;
> public static void main(String [] args) {
> System.out.println("HELLO: args = " + args);
> }
> }
>
> If your compiler can find "import java.awt.Frame", then it can find
> java.awt.Frame without the import. You don't need import, it just allows
> you to shorten the FQN to just the class name.

I think a better solution would be to rename foo.bar.Frame. If it did
not have some functional difference from java.awt.Frame, it would not
exist. Presumably, it is Frame specialized in some way, and its name
should indicate that specialization.

Patricia

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#13486

On 4/11/2012 9:34 AM, Patricia Shanahan wrote:

> I think a better solution would be to rename foo.bar.Frame. If it did
> not have some functional difference from java.awt.Frame, it would not
> exist. Presumably, it is Frame specialized in some way, and its name
> should indicate that specialization.


Well, its full name "foo.bar.Frame" should indicate its specialization. 
  A better name like com.application.main.Frame would be a more likely 
choice if this weren't a quick example on the internet.  In general I 
don't have a problem with using common words as class names in different 
packages.  It actually adds to clarity in many cases.

OTOH, if the actual use of foo.bar.Frame and java.awt.Frame gets to be a 
pain to deal with, then it certainly should be renamed.  Confusion or 
even just convenience is a sufficient reason for refactoring the name of 
a class.

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#13487

On 4/11/12 4:56 AM, Maciej Labanowicz wrote:
> Hi,
>
> I'm trying to compile simple class, named Frame in package foo.bar:
>
> --[beg]--[Frame.java]-----------------------------------
> package foo.bar;
> import  java.awt.Frame;
> public class Frame extends java.awt.Frame {
>    public static final long serialVersionUID = 1L;
>    public static void main(String [] args) {
>      System.out.println("HELLO: args = " + args);
>    }
> }
> --[eof]--[Frame.java]-----------------------------------
As others have pointed out, the problem is that you import Frame.  you 
don't need to import something if you use the fully qualified name.

A side note, extending Frame is probably not what you really want to do. 
It is unfortunate that so many examples and tutorials have you do this, 
but in reality, you just need to compose a Frame with the various 
Components you need.  For the most part, the only time you need to 
extend *any* Component or JComponent is when you are creating a custom 
view of a specific type of data. And then you should only extend 
JComponent or Canvas as I understand it.


hth,
Daniel.

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#13488

Daniel Pitts wrote:
> Maciej Labanowicz wrote:
>> I'm trying to compile simple class, named Frame in package foo.bar:
>>
>> --[beg]--[Frame.java]-----------------------------------
>> package foo.bar;
>> import  java.awt.Frame;
>> public class Frame extends java.awt.Frame {
>>    public static final long serialVersionUID = 1L;
>>    public static void main(String [] args) {
>>      System.out.println("HELLO: args = " + args);
>>    }
>> }
>> --[eof]--[Frame.java]-----------------------------------

> As others have pointed out, the problem is that you import Frame.  you 
> don't need to import something if you use the fully qualified name.
> 
> A side note, extending Frame is probably not what you really want to do. 
> It is unfortunate that so many examples and tutorials have you do this, 
> but in reality, you just need to compose a Frame with the various 
> Components you need.  For the most part, the only time you need to 
> extend *any* Component or JComponent is when you are creating a custom 
> view of a specific type of data. And then you should only extend 
> JComponent or Canvas as I understand it.

This raises another question, OP: Why do you use 'java.awt.Frame' instead of 'javax.swing.JFrame'?

-- 
Lew

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