LinuxQuestions.org - set java classpath on linux

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set java classpath on linux

Hello!
I'm a new user in Linux. I'm using opensuse 11.2, but i don't know how to set path to java. The problem in console:

Code:

Exception in thread "main" java.lang.NoClassDefFoundError: myfirstprogram

Caused by: java.lang.ClassNotFoundException: myfirstprogram

        at java.net.URLClassLoader$1.run(URLClassLoader.java:217)

        at java.security.AccessController.doPrivileged(Native Method)

        at java.net.URLClassLoader.findClass(URLClassLoader.java:205)

        at java.lang.ClassLoader.loadClass(ClassLoader.java:323)

        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)

        at java.lang.ClassLoader.loadClass(ClassLoader.java:268)

        at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:336)

Could not find the main class: myfirstprogram. Program will exit.

Is this echo $PATH? Where it have to be wrote?

Quote:

Is this echo $PATH? Where it have to be wrote?

No, it's not. Test it, enter this in the console:

Quote:

java -version

...there should be some info comming back.

The line to worry about is:

Quote:

java.lang.NoClassDefFoundError

...you're using something that java cannot find. The path has to be set to that component as well...

Happy coding! :)

Thor

Java searches its CLASSPATH for classes; nothing to do with the shell's path. From man java:

Code:

          -classpath classpath



          -cp classpath

            Specify a list of directories, JAR archives, and ZIP archives to search for class files. Class path entries are

            separated by colons (:). Specifying -classpath or -cp overrides any setting of the CLASSPATH environment variable.



          If -classpath and -cp are not used and CLASSPATH is not set, the user class path consists of the current directory

          (.).

So you either set CLASSPATH=/your/path in the shell or you add -classpath or -cp to the java command.

How I can to find the Classpath? Give me an example.

Find it with:

Quote:

echo $CLASSPATH

set it (as SecretCode pointed out) like so

Quote:

CLASSPATH=/some/path;some/other/path

This can be persisted if you add this (last) line to, say, /etc/rc.conf - depending on your distro, on OpenSuse, you may need to look into the /etc/rc.d folder instead...

Thor

Who is the quick CLASSPATH?
echo $CLASSPATH is empty!

It depends where you have installed java and more importantly where your code is.

Your error says it can't find myfirstprogram so you need to give the location of myfirstprogram.class - either in $CLASSPATH or on the java command line

linux-kzpj:/home/denislav/Desktop # CLASSPATH=/home/denislav/Download/;/home/denislav/Desktop/myfirstjavaprog.java
bash: /home/denislav/Desktop/myfirstjavaprog.java: Permission denied

OR

linux-kzpj:/home/denislav/Desktop # java /home/denislav/Desktop/myfirstjavaprog /home/denislav/Desktop/myfirstjavaprog.class
Exception in thread "main" java.lang.NoClassDefFoundError: /home/denislav/Desktop/myfirstjavaprog
Caused by: java.lang.ClassNotFoundException: .home.denislav.Desktop.myfirstjavaprog
at java.net.URLClassLoader$1.run(URLClassLoader.java:217)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
at java.lang.ClassLoader.loadClass(ClassLoader.java:323)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
at java.lang.ClassLoader.loadClass(ClassLoader.java:268)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:336)
Could not find the main class: /home/denislav/Desktop/myfirstjavaprog. Program will exit.

My myfrsjavaprog is in /home/denislav/Desktop/myfirstjavaprog.java What I have to make?

Quote:

Originally Posted by rotation (Post 4531910)

Hi,

try quoting your classpath variable:

Code:

CLASSPATH="/home/denislav/Download/;/home/denislav/"

Alternatively, you can call your program like:

Code:

java -cp /home/denislav/Desktop/ myfirstjavaprog

Notice, that your CLASSPATH contains the directory where your program resides; the name of the program is not part of the classpath.

denislav@linux-kzpj:~/Desktop> java -cp /home/denislav/Desktop/ myfirstjavaprog
Exception in thread "main" java.lang.UnsupportedClassVersionError: myfirstjavaprog : Unsupported major.minor version 51.0
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:637)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:277)
at java.net.URLClassLoader.access$000(URLClassLoader.java:73)
at java.net.URLClassLoader$1.run(URLClassLoader.java:212)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
at java.lang.ClassLoader.loadClass(ClassLoader.java:323)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
at java.lang.ClassLoader.loadClass(ClassLoader.java:268)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:336)
Could not find the main class: myfirstjavaprog. Program will exit.

Any idea?

Lots of web search results for "UnsupportedClassVersionError". You may have an older Java version on the host where you are trying to run this.

What do you get from

Code:

java -version

denislav@linux-kzpj:~> java -version
java version "1.6.0_0"
OpenJDK Runtime Environment (IcedTea6 1.6) (suse-5.9.4-i386)
OpenJDK Server VM (build 14.0-b16, mixed mode)

And did you compile the myfirstjavaprog class using a later compiler version? That message is saying that somehow myfirstjavaprog.class expects a higher java runtime version than you are running it with.

Do you have a $JAVA_HOME environment variable set?

Code:

denislav@linux-kzpj:~/Desktop> $JAVA_HOME

Usage: java [-options] class [args...]

          (to execute a class)

  or  java [-options] -jar jarfile [args...]

          (to execute a jar file)

where options include:

    -d32          use a 32-bit data model if available

    -d64          use a 64-bit data model if available

    -client          to select the "client" VM

    -server          to select the "server" VM

    -hotspot          is a synonym for the "client" VM  [deprecated]

                  The default VM is server,

                  because you are running on a server-class machine.





    -cp <class search path of directories and zip/jar files>

    -classpath <class search path of directories and zip/jar files>

                  A : separated list of directories, JAR archives,

                  and ZIP archives to search for class files.

    -D<name>=<value>

                  set a system property

    -verbose[:class|gc|jni]

                  enable verbose output

    -version      print product version and exit

    -version:<value>

                  require the specified version to run

    -showversion  print product version and continue

    -jre-restrict-search | -jre-no-restrict-search

                  include/exclude user private JREs in the version search

    -? -help      print this help message

    -X            print help on non-standard options

    -ea[:<packagename>...|:<classname>]

    -enableassertions[:<packagename>...|:<classname>]

                  enable assertions with specified granularity

    -da[:<packagename>...|:<classname>]

    -disableassertions[:<packagename>...|:<classname>]

                  disable assertions with specified granularity

    -esa | -enablesystemassertions

                  enable system assertions

    -dsa | -disablesystemassertions

                  disable system assertions

    -agentlib:<libname>[=<options>]

                  load native agent library <libname>, e.g. -agentlib:hprof

                  see also, -agentlib:jdwp=help and -agentlib:hprof=help

    -agentpath:<pathname>[=<options>]

                  load native agent library by full pathname

    -javaagent:<jarpath>[=<options>]

                  load Java programming language agent, see java.lang.instrument

    -splash:<imagepath>

                  show splash screen with specified image

See http://java.sun.com/javase/reference for more details.

Quote:

Originally Posted by rotation (Post 4534565)

denislav@linux-kzpj:~/Desktop> $JAVA_HOME
Usage: ...

1: Always remember to use [code][/code] tags around your code

2: When you want to find out the value of an environment variable, use echo

Code:

echo $JAVA_HOME

What you've done is to execute the contents which could have been very dangerous!