Raspberry Pi Forums

Hi,

I am relatively new to using the Raspberry Pi and Java so I apologise if the answer to my issue appears obvious to you all. I installed Java using:
sudo apt-get update && sudo apt-get install oracle-java7-jdk

When I check the version installed via terminal I get the following outputs:
pi@raspberrypi ~ $ java -version
java version "1.6.0_27"
OpenJDK Runtime Environment (IcedTea6 1.12.6) (6b27-1.12.6-1~deb7u1+rpi1) OpenJDK Zero VM (build 20.0-b12, mixed mode)

pi@raspberrypi ~ $ javac -version
javac 1.7.0_40

I wrote a simple java file called HelloWorld and compiled the file. However when I try to execute the script I get the following error message:

pi@raspberrypi ~ $ java HelloWorld
Exception in thread "main" java.lang.UnsupportedClassVersionError: HelloWorld : Unsupported major.minor version 51.0
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:634)
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$1.run(URLClassLoader.java:212)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
Could not find the main class: HelloWorld. Program will exit.


I've Googled the error and found various suggestions to resolve the issue; however some of these solutions are for different operating systems, devices and versions of Java. I don’t want to damage anything and feel like I’m guessing.

I’d appreciate it if someone could offer a solution or direct me to a post I’ve missed that can walk me through what I need to do.

My operating system is Rasbian Weezy.

Thanks in advance

Sorry, my post took a few hours to be approved and in the mean time I think I found a solution.

I used the instructions from point 7 of the post below:

http://stackoverflow.com/questions/1058 ... -on-ubuntu

I think that the issue that I had Java version 1.6.0 and Javac version 1.7.0

If I'm wrong and just got lucky I'd still appreciate an explanation from those in then know.

That Java error mean you are trying to execute class files compiled with a X version of java, in a Y java virtual machine. When X version (compile) > Y version (vm)

When you execute java -version, the virtual machine, you get the 1.6
When you execute javac -version, the compiler, you get the 1.7

You are trying to execute 1.7 compiled class in a 1.6 vm. As you have said, that is the problem.


The solution is quite simple, you need to use the same java version in executing and compiling. I think you may have something wrong with the path in the raspberry system. I do not use java in the raspberry, so with this concrete subject I am afraid I cannot help you.

But in the other hand, when you compile the class files, you can use the javac -target 6 option. With this you can generate class files to run with a lower vm version.

Hope this will be helpful