Some newbie questions

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SteM - 15 Nov 2007 17:13 GMT

Hi all,
i need to understand some points about java:

1. how can i know which jres are installed on my PC (Windows)?
1.1 how can i know which is the currently selected as default?

2. can i select one of them on the command line launching an application to
be sure it will run on the wanted VM? I mean something like 'java -jar
myapp.jar -ver1.6', even if the 1.6 is not the currently selected jvm as
default.

3. I have two jar files: with the command line i run the first; it is
possible to launch programmately the second jar from the first jar code?

Thanks a lot !!
--
SteM

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Andrew Thompson - 15 Nov 2007 17:33 GMT

...

>1. how can i know which jres are installed on my PC (Windows)?

<http://java.sun.com/products/javawebstart/apps/player.jnlp>
Close the 'Java Cache Viewer' and change to the
'Java' tab of the 'Java Control Panel'.
There you can 'View' the JREs, and in the case of the
'Java Application Runtime Settings', also 'Find' others
not listed.

>1.1 how can i know which is the currently selected as default?

The default used, will most probably be the highest version
Java listed and ticked as being 'enabled'. You can check
it for either browser or application, here..
<http://www.physci.org/jws/#jtest>

>2. can i select one of them on the command line launching an application to
>be sure it will run on the wanted VM? I mean something like 'java -jar
>myapp.jar -ver1.6', even if the 1.6 is not the currently selected jvm as
>default.

Not easily - not to my knowledge.

Java Web Start (the thing that launched the Java Control Panel
above) can do versioning for an application with a GUI.
<http://www.physci.org/jws/version.html>

Will your application have a GUI?

>3. I have two jar files: with the command line i run the first; it is
>possible to launch programmately the second jar from the first jar code?

Yep.

BTW - Please start sentences with a single upper-case
letter, and note that the word 'I' is always upper-case in
English, *always*.

Signature

Andrew Thompson
http://www.athompson.info/andrew/

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SteM - 15 Nov 2007 17:56 GMT

> ..
> >1. how can i know which jres are installed on my PC (Windows)?
[quoted text clipped - 5 lines]
> 'Java Application Runtime Settings', also 'Find' others
> not listed.

Yes, sorry, I meant by program, I guess I have to enum
HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\Java Runtime Environment registry keys
....

> >1.1 how can i know which is the currently selected as default?
>
> The default used, will most probably be the highest version
> Java listed and ticked as being 'enabled'. You can check
> it for either browser or application, here..
> <http://www.physci.org/jws/#jtest>

Ok, but also with 'java -version'

> >2. can i select one of them on the command line launching an application to
> >be sure it will run on the wanted VM? I mean something like 'java -jar
> >myapp.jar -ver1.6', even if the 1.6 is not the currently selected jvm as
> >default.
>
> Not easily - not to my knowledge.

It seems that 'java -version:xxx ...' selects a certain jre version....

> >3. I have two jar files: with the command line i run the first; it is
> >possible to launch programmately the second jar from the first jar code?
>
> Yep.

A little help .....? :-)

> BTW - Please start sentences with a single upper-case
> letter, and note that the word 'I' is always upper-case in
> English, *always*.

Yes, you are right, sorry :-)
--
SteM

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