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java Environment in Manjaro Linux

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  java Environment in Manjaro Linux ruben <ceo@iran.gov> - 2016-01-22 15:37 +0000
    Re: java Environment in Manjaro Linux Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-01-22 11:16 -0500
    Re: java Environment in Manjaro Linux Martin Gregorie <martin@address-in-sig.invalid> - 2016-01-22 20:44 +0000
      Re: java Environment in Manjaro Linux ruben <ceo@iran.gov> - 2016-01-22 21:10 +0000
        Re: java Environment in Manjaro Linux Martin Gregorie <martin@address-in-sig.invalid> - 2016-01-22 22:25 +0000
          Re: java Environment in Manjaro Linux Martin Gregorie <martin@address-in-sig.invalid> - 2016-01-22 23:11 +0000
    Re: java Environment in Manjaro Linux Arne Vajhøj <arne@vajhoej.dk> - 2016-01-22 20:45 -0500
      Re: java Environment in Manjaro Linux Martin Gregorie <martin@address-in-sig.invalid> - 2016-01-23 11:17 +0000

#33511 — java Environment in Manjaro Linux

I'm testing the java developers environment and its not working as I 
expected

[ruben@localhost cs664s16]$ cat ./helloworld.java 
public class helloworld {
   public static void main(String[] args) {
         System.out.println("Bonjour le monde !");
 }

}


[ruben@localhost cs664s16]$ echo $CLASSPATH
/home/ruben/GNUstep/Library/Libraries/Java:/root/GNUstep/Library/
Libraries/Java:/usr/lib/GNUstep/Libraries/Java:.:./


[ruben@localhost cs664s16]$ java ./helloworld.java 
Error: Could not find or load main class ..helloworld.java


this works however:

[ruben@localhost cs664s16]$ java helloworld
Bonjour le monde !



So, I am completely confused.  How can it not take the specified file 
name to run?

Also, where is the $CLASSPATH set?  in the system /etc/profile ?  I 
should probaly add ./ to the bashrc file?

Ruben

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#33514

On 1/22/2016 10:37 AM, ruben wrote:
> I'm testing the java developers environment and its not working as I
> expected
>
> [ruben@localhost cs664s16]$ cat ./helloworld.java
> public class helloworld {
>     public static void main(String[] args) {
>           System.out.println("Bonjour le monde !");
>   }
>
> }
>
>
> [ruben@localhost cs664s16]$ echo $CLASSPATH
> /home/ruben/GNUstep/Library/Libraries/Java:/root/GNUstep/Library/
> Libraries/Java:/usr/lib/GNUstep/Libraries/Java:.:./
>
>
> [ruben@localhost cs664s16]$ java ./helloworld.java
> Error: Could not find or load main class ..helloworld.java
>
>
> this works however:
>
> [ruben@localhost cs664s16]$ java helloworld
> Bonjour le monde !
>
>
>
> So, I am completely confused.  How can it not take the specified file
> name to run?

     `helloworld.java' is a source file full of Java source code.
The corresponding class file (produced by the javac compiler) would
be `helloworld.class'.  If you're familiar with languages like C or
C++, this is similar to the distinction between `helloworld.c' and
`helloworld.o'.

     Furthermore, the java command itself doesn't want either file
name: It just wants the class name `helloworld', and it knows to
look for `helloworld.class' in "various places."  In your case it
will find `helloworld.class' as an ordinary file in one of the
directories listed in CLASSPATH, but there are other possibilities
that can be used in other setups.  It might find `helloworld.class'
as one member of a "jar file" (a specially-formatted ZIP archive),
or it might be told to load `helloworld.class' from the network,
and still other even more exotic setups can be concocted.  The
upshot, though, it that you tell Java the unadorned class name,
not the name of a file.

> Also, where is the $CLASSPATH set?  in the system /etc/profile ?  I
> should probaly add ./ to the bashrc file?

     Sorry; I have no idea what piece of script sets your CLASSPATH.

-- 
esosman@comcast-dot-net.invalid
"Don't be afraid of work. Make work afraid of you." -- TLM

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#33516

On Fri, 22 Jan 2016 15:37:43 +0000, ruben wrote:

> I'm testing the java developers environment and its not working as I
> expected
> 
> [ruben@localhost cs664s16]$ cat ./helloworld.java public class
> helloworld {
>    public static void main(String[] args) {
>          System.out.println("Bonjour le monde !");
>  }
> 
> }
> 
> 
> [ruben@localhost cs664s16]$ echo $CLASSPATH
> /home/ruben/GNUstep/Library/Libraries/Java:/root/GNUstep/Library/
> Libraries/Java:/usr/lib/GNUstep/Libraries/Java:.:./
> 
> 
> [ruben@localhost cs664s16]$ java ./helloworld.java Error: Could not find
> or load main class ..helloworld.java
>
You don't show how you compiled the source file.

> 
> this works however:
> 
> [ruben@localhost cs664s16]$ java helloworld Bonjour le monde !
> 
In that case helloworld.class, as output by the compiler, must be in 
CLASSPATH somewhere.

what does "ls" show when run in the directory holding helloworld.java?

what does "sudo updatedb; locate helloworld.class" show? Be patient: it 
make take a few minutes to run if you haven't run updatedb recently.


-- 
martin@   | Martin Gregorie
gregorie. | Essex, UK
org       |

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#33517

On Fri, 22 Jan 2016 20:44:42 +0000, Martin Gregorie wrote:


> You don't show how you compiled the source file.
> 

with javac

> 
>> this works however:
>> 
>> [ruben@localhost cs664s16]$ java helloworld Bonjour le monde !
>> 
> In that case helloworld.class, as output by the compiler, must be in
> CLASSPATH somewhere.
>
yes

 
> what does "ls" show when run in the directory holding helloworld.java?
>

 [ruben@localhost cs664s16]$ ls -l
total 20
-rw-r--r-- 1 ruben users 432 Jan 22 10:30 helloworld.class
-rw-r--r-- 1 ruben users 127 Jan 22 10:30 helloworld.java
-rw-r--r-- 1 ruben users 430 Jan 22 10:46 Main.class
-rw-r--r-- 1 ruben users 173 Jan 22 09:43 Main.java
-rw-r--r-- 1 ruben users  28 Jan 22 08:47 README.md

> what does "sudo updatedb; locate helloworld.class" show? Be patient: it
> make take a few minutes to run if you haven't run updatedb recently.

locate/updatedb will not search my home directory, in my setup, 
regardless how often it runs


[ruben@localhost cs664s16]$ find /home/ruben/ -iname "helloworld*" -print
/home/ruben/src/grad_school/compiler/cs664s16/helloworld.class
/home/ruben/src/grad_school/compiler/cs664s16/helloworld.java
/home/ruben/.cpan/build/Perl6-Pugs-6.2.13-PTKdk7/ext/WTemplate/examples/
helloworld.tpl
/home/ruben/.cpan/build/Perl6-Pugs-6.2.13-PTKdk7/ext/WTemplate/examples/
helloworld.pl
/home/ruben/.cpan/build/Perl6-Pugs-6.2.13-PTKdk7/misc/pX/Common/AST-
Design/Perl5/helloworld.in
/home/ruben/.eclipse/
org.eclipse.platform_4.4.2_1543616141_linux_gtk_x86_64/configuration/
org.eclipse.osgi/152/0/.cp/cheatsheets/HelloWorld.xml
/home/ruben/.eclipse/
org.eclipse.platform_4.4.2_1543616141_linux_gtk_x86_64/configuration/
org.eclipse.osgi/152/0/.cp/cheatsheets/HelloWorldSWT.xml
/home/ruben/.eclipse/
org.eclipse.platform_4.4.2_1543616141_linux_gtk_x86_64/configuration/
org.eclipse.osgi/190/0/.cp/cheatsheets/helloworld-composite.xml
/home/ruben/.eclipse/
org.eclipse.platform_4.4.2_1543616141_linux_gtk_x86_64/configuration/
org.eclipse.osgi/190/0/.cp/cheatsheets/helloworld
/home/ruben/.eclipse/
org.eclipse.platform_4.4.2_1543616141_linux_gtk_x86_64/configuration/
org.eclipse.osgi/190/0/.cp/cheatsheets/helloworld/helloworld-feature.xml
/home/ruben/.eclipse/
org.eclipse.platform_4.4.2_1543616141_linux_gtk_x86_64/configuration/
org.eclipse.osgi/190/0/.cp/cheatsheets/helloworld/helloworld-create.xml
/home/ruben/.eclipse/
org.eclipse.platform_4.4.2_1543616141_linux_gtk_x86_64/configuration/
org.eclipse.osgi/190/0/.cp/cheatsheets/helloworld/helloworld-install.xml
/home/ruben/.eclipse/
org.eclipse.platform_4.4.2_1543616141_linux_gtk_x86_64/configuration/
org.eclipse.osgi/190/0/.cp/cheatsheets/helloworld/helloworld-extension.xml
/home/ruben/.eclipse/
org.eclipse.platform_4.4.2_1543616141_linux_gtk_x86_64/configuration/
org.eclipse.osgi/190/0/.cp/cheatsheets/helloworld/helloworld-update.xm

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#33521

On Fri, 22 Jan 2016 21:10:46 +0000, ruben wrote:

> On Fri, 22 Jan 2016 20:44:42 +0000, Martin Gregorie wrote:
> 
> 
>> You don't show how you compiled the source file.
>> 
>> 
> with javac
>
OK
 
>> what does "ls" show when run in the directory holding helloworld.java?
>>
>>
>  [ruben@localhost cs664s16]$ ls -l
> total 20 -rw-r--r-- 1 ruben users 432 Jan 22 10:30 helloworld.class
> -rw-r--r-- 1 ruben users 127 Jan 22 10:30 helloworld.java -rw-r--r-- 1
> ruben users 430 Jan 22 10:46 Main.class -rw-r--r-- 1 ruben users 173 Jan
> 22 09:43 Main.java -rw-r--r-- 1 ruben users  28 Jan 22 08:47 README.md
>
OK, so javac is working as expected and putting the .class file alongside 
the .java file it was compiled from.

Note that none of  

  java helloworld.java 
  java helloworld.class 
  java ./helloworld 

will run on my system either because 'java' it is using the name as a 
class name, which in your class is simply 'helloworld', and searching 
through CLASSPATH and the current directory for it.
 
>> what does "sudo updatedb; locate helloworld.class" show? Be patient: it
>> make take a few minutes to run if you haven't run updatedb recently.
> 
> locate/updatedb will not search my home directory, in my setup,
> regardless how often it runs
>
How odd.
 

-- 
martin@   | Martin Gregorie
gregorie. | Essex, UK
org       |

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#33522

On Fri, 22 Jan 2016 22:25:46 +0000, Martin Gregorie wrote:

> Note that none of
> 
>   java helloworld.java 
>   java helloworld.class 
>   java ./helloworld
> 
> will run on my system either because 'java' it is using the name as a
> class name, which in your class is simply 'helloworld', and searching
> through CLASSPATH and the current directory for it.
>  
However, something like this:

   java -classpath /home/kiwi/compiler_tests/hello_world helloworld

does work because its redefined the classpath to be just:
 
   the standard Java SE class library 
   /home/kiwi/compiler_tests/hello_world
 

-- 
martin@   | Martin Gregorie
gregorie. | Essex, UK
org       |

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#33523

On 1/22/2016 10:37 AM, ruben wrote:
> Also, where is the $CLASSPATH set?  in the system /etc/profile ?  I
> should probaly add ./ to the bashrc file?

I will recommend against using CLASSPATH env var.

Arne

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#33524

On Fri, 22 Jan 2016 20:45:31 -0500, Arne Vajhøj wrote:

> On 1/22/2016 10:37 AM, ruben wrote:
>> Also, where is the $CLASSPATH set?  in the system /etc/profile ?  I
>> should probaly add ./ to the bashrc file?
> 
> I will recommend against using CLASSPATH env var.
>
Agreed - sort of. I find $CLASSPATH convenient during development, but 
almost always end up running developed, live code from a bash script that 
sets the java -classpath option.
 

-- 
martin@   | Martin Gregorie
gregorie. | Essex, UK
org       |

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