Thanks, my little test case was bogus, it did not illustrate the
bug that I was having.
It turns out that the problem was somewhat more complex.
In Ptolemy II, we have a Nameable interface which is implemented
by a NamedObj class. A NamedList is a list of NamedObjs.
The NamedList class has a method get(), which returns
a Nameable Object.
The problem was that when I upgraded to Tcl Blend 1.1,
I needed to use java::cast to get back my original object
Here, I create a NamedList and then prepend a NamedObj
% set dir [java::new ptolemy.kernel.util.NamedList]
java0x6
% set n1 [java::new ptolemy.kernel.util.NamedObj "n1"]
java0x7
% $dir prepend $n1
Now, when I get from the NamedList, I get a Nameable, which
is not exactly the same as what I passed in.
% set n1New [$dir get "n1"]
java0x8
% java::info class $n1New
ptolemy.kernel.util.Nameable
% java::info class $n1
ptolemy.kernel.util.NamedObj
However, if I cast the return value to Nameable, then it does work!
% set n1New2 [java::cast ptolemy.kernel.util.NamedObj [$dir get "n1"]]
java0x7
% set n1New2 [java::cast ptolemy.kernel.util.NamedObj [$dir get "n1"]]
java0x7
%
Under Tcl Blend 1.0, the java::cast command did not exist, and
it was not necessary. What I got back was exactly what I passed in.
A couple of hints in general:
1) One of our group members pointed out that in general, if you plan
on using a return value, then you should set a Tcl variable
Here, everytime we call getPort, we get a new Object
% $bar getPort output
java0x3
% $bar getPort output
java0x4
Here, the value is saved for us.
% set p1 [$bar getPort output]
java0x5
% set p2 [$bar getPort output]
java0x5
It seems that under Jacl, objects that are not saved to Tcl
variables have very short lifetimes, whereas under Tcl Blend, I've
seen objects persist for a little while before being garbage
collected.
2) Really, what I wanted to do here was use the Object.equals()
method to compare the value I pushed on to the list to the
value I pulled back off. Instead, I was just comparing
the java0x values, which is not the right thing to do.
3) java::info class is your friend :-)
-Christopher
--------
On Thu, 18 Mar 1999, Christopher Hylands wrote:
> It looks like Tcl Blend is returning a new value everytime I do a
> get() on a LinkedList. This is confusing because Java returns the
> same value that I passed in to the list
>
> In this simple Java class, I create a LinkedList, then add a
> GregorianCalendar to the list. When I get the GregorianCalendar
> object back from the List, it is a pointer to the same object as
> what I passed in.
>
>
> bash-2.02$ cat T.java
> import java.util.*;
> public class T {
> static void main(String v[]) {
> LinkedList l = new LinkedList();
> GregorianCalendar cal = new java.util.GregorianCalendar();
> l.add(0, cal);
> System.out.println( (cal == l.get(0)));
> }
> }
> bash-2.02$ javac T.java
> bash-2.02$ java T
> true
>
>
> In this Tcl Blend 1.1.1 version with JDK1.2 under NT4, the java0x
> value that I get back from the list is not the same as what I passed
> in. Note that each time I call get, I get a different java0x value.
> I believe that Under Tcl Blend 1.0, I got the same value as what I
> passed in.
Whoops, looks like you forgot to put a $ in front of that
variable.
Good:
$l add 0 $cal
Bad:
$l add 0 cal
That would explain your problem as the string "cal" would
have gotten converted to a java.lang.String object.
Here is my version which seems to work just fine.
package require java
set l [java::new java.util.LinkedList]
set cal [java::new java.util.GregorianCalendar]
$l add 0 $cal
set tmpcal [java::cast java.util.GregorianCalendar [$l -noconvert get 0]]
expr {$tmpcal == $cal}
# returns 1
later
mo
>
> bash-2.02$ cat /tmp/t.tcl
> set l [java::new java.util.LinkedList]
> set cal [java::new java.util.GregorianCalendar]
> $l add 0 cal
> puts "[expr { $cal == [$l -noconvert get 0]}]"
> puts "cal = $cal"
> puts "\[$l get 0\] = [$l -noconvert get 0]"
> puts "\[$l get 0\] = [$l -noconvert get 0]"
> bash-2.02$
>
>
> bash-2.02$ tclsh80
> sourcing /users/cxh/tclshrc.tcl
> % package require java
> 1.1.1
> % source /tmp/t.tcl
> 0
> cal = java0x2
> [java0x1 get 0] = java0x4
> [java0x1 get 0] = java0x5
> %
>
> -Christopher
>
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