Java Problem java.lang.UnsupportedClassVersionError

A way better Question: How can i fix it? :)

Try to recompile the java file with Sun's javac:
javac MyClass.java

Unfortunately this didn't make any difference. I changed my java sdk version. Also not solving this. Just a slightly different Error Message:

foo@bar:~/NetBeans/javaRegEx/src/javaregex$ ls
Main.java
foo@bar:~/NetBeans/javaRegEx/src/javaregex$ javac Main.java
foo@bar:~/NetBeans/javaRegEx/src/javaregex$ ls
Main.class Main.java
foo@bar:~/NetBeans/javaRegEx/src/javaregex$ java Main
Exception in thread "main" java.lang.UnsupportedClassVersionError: Main (Unsupported major.minor version 50.0)
        at java.lang.ClassLoader.defineClass0(Native Method)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:539)
        at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:123)
        at java.net.URLClassLoader.defineClass(URLClassLoader.java:251)
        at java.net.URLClassLoader.access$100(URLClassLoader.java:55)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:194)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:187)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:289)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:274)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:235)
        at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:302)

foo@bar:~/NetBeans/javaRegEx/src/javaregex$ java -version
java version "1.4.2-02"
Java(TM) 2 Runtime Environment, Standard Edition (build Blackdown-1.4.2-02)
Java HotSpot(TM) Client VM (build Blackdown-1.4.2-02, mixed mode)

Well i copied this Example code from a sun Documentation... Maybe this doesn't work:

import java.io.Console;
import java.util.regex.Pattern;
import java.util.regex.Matcher;

well. your sun java is not called.

you need to execute

 sudo update-alternatives --config java

and then select the sun java version

java -version should then give you the version of the sun java (java version "1.5.0_11")

You also might want to change the priority of the vm by editing the file /etc/jvm and put the line

/usr/lib/jvm/java-1.5.0-sun

in the front of the other lines.

I hope this solves your problem

I think i got a Solution for that one:

sudo update-alternatives --config java

AND

sudo update-alternatives --config javac

--> They must be set to the same Java Version.

i am getting the same problem when i am running simple java applications. I have jdk 1.5_08 installed in my system
Tried running this command,but when I am trying to run this in commandprompt...its showing 'sudo' is not recognised as an internal or external command,operable program or batch file. please help me get rid of this problem. Thats why i am not able to run it in eclipse also.

Thank you for this thread. I had the same trouble. But after running
sudo update-alternatives --config java
sudo update-alternatives --config javac
as a-r-k-i-b-o-t-t said and assuring the both use the same Java Version all worked perfectly.