javac file has wrong version 51.0, should be 49.0

[Michael Pope]

I'm running Debian stable (7.6) 64bit and have installed Oracle JDK 7
manually under /opt/jdk1.7.0, this has been running programs for a while
and that still works. What is broken though is I cannot compile
something with javac.

If I run javac HelloWorldApp.java I get the following error
HelloWorldApp.java:5: cannot access java.lang.Object
bad class file: /opt/jdk1.7.0/jre/lib/rt.jar(java/lang/Object.class)
class file has wrong version 51.0, should be 49.0
Please remove or make sure it appears in the correct subdirectory of the
classpath.
class HelloWorldApp {
^
1 error

Here is the code;
/**
* The HelloWorldApp class implements an application that
* simply displays "Hello World!" to the standard output.
*/
class HelloWorldApp {
public static void main(String[] args) {
System.out.println("Hello World!"); //Display the string.
}
}


They are the same version

$ java -version
java version "1.7.0"
Java(TM) SE Runtime Environment (build 1.7.0-b147)
Java HotSpot(TM) 64-Bit Server VM (build 21.0-b17, mixed mode)

$ javac -version HelloWorldApp.java
javac 1.7.0

They point to the same area

$ update-alternatives --display java
java - auto mode
link currently points to /opt/jdk1.7.0/bin/java
/opt/jdk1.7.0/bin/java - priority 1065
/usr/lib/jvm/java-6-openjdk-amd64/jre/bin/java - priority 1061
slave java.1.gz: /usr/lib/jvm/java-6-openjdk-amd64/jre/man/man1/java.1.gz
/usr/lib/jvm/java-7-openjdk-amd64/jre/bin/java - priority 1051
slave java.1.gz: /usr/lib/jvm/java-7-openjdk-amd64/jre/man/man1/java.1.gz
Current 'best' version is '/opt/jdk1.7.0/bin/java'.

$ update-alternatives --display javac
javac - auto mode
link currently points to /opt/jdk1.7.0/bin/javac
/opt/jdk1.7.0/bin/javac - priority 1065
Current 'best' version is '/opt/jdk1.7.0/bin/javac'.



--
from
Michael

[Darren Wurf]

On Tue, Nov 25, 2014 at 12:55 PM, Michael Pope <map...@gmail.com> wrote:
> If I run javac HelloWorldApp.java I get the following error
> HelloWorldApp.java:5: cannot access java.lang.Object
> bad class file: /opt/jdk1.7.0/jre/lib/rt.jar(java/lang/Object.class)
> class file has wrong version 51.0, should be 49.0
>

I'm guessing you have a JDK1.5 installed on your system[1]. For
whatever reason, that's getting involved in the compilation process.
Try using the full path to javac, do you get the same result?

Cheers,

Darren

[1] http://java67.blogspot.com.au/2012/10/how-to-fix-javalangunsupportedclassversionerror-major-minor-version-49-50-51.html

[Darren Wurf]

Oh, and don't forget to:
export JAVA_HOME=/opt/jdk1.7.0/

--
Darren

[Michael Pope]

I don't have Java 5 or 6 installed, I just have two versions OpenJDK-7 &
Oracle-7-Java.

I do have JAVA_HOME=/opt/jdk1.7.0 and it still results in the same error
message when compiling. I've gone to the extent now of creating a VM and
building it (with ansible scripts) the same as my server and it works.
So now I'm comparing the two. It doesn't make any sense.



from
Michael

[Darren Wurf]

Hmm. This error seems to indicate you're accessing a java7 copy of the
JRE standard libs from a java5 environment. Check your environment
variables for any java-related stuff, maybe some variable is
triggering cross-compilation. Scan your drive for rogue JVMs/JDKs
installed by other software (eg eclipse-based stuff, proprietary java
apps, other Java-dependent IDEs, etc etc)

Cheers,

--
Darren

[Michael Pope]

I just got it working by cheating off my VM install and changing the
javac to the following
sudo update-alternatives --set javac
/usr/lib/jvm/java-7-openjdk-amd64/bin/javac

lrwxrwxrwx 1 root root 22 Jun 7 2013 /etc/alternatives/java ->
/opt/jdk1.7.0/bin/java
lrwxrwxrwx 1 root root 43 Nov 25 15:51 /etc/alternatives/javac ->
/usr/lib/jvm/java-7-openjdk-amd64/bin/javac
lrwxrwxrwx 1 root root 45 Nov 25 15:47 /etc/alternatives/javadoc ->
/usr/lib/jvm/java-7-openjdk-amd64/bin/javadoc
lrwxrwxrwx 1 root root 55 Nov 25 15:47 /etc/alternatives/javadoc.1.gz ->
/usr/lib/jvm/java-7-openjdk-amd64/man/man1/javadoc.1.gz
lrwxrwxrwx 1 root root 43 Nov 25 15:47 /etc/alternatives/javah ->
/usr/lib/jvm/java-7-openjdk-amd64/bin/javah
lrwxrwxrwx 1 root root 53 Nov 25 15:47 /etc/alternatives/javah.1.gz ->
/usr/lib/jvm/java-7-openjdk-amd64/man/man1/javah.1.gz
lrwxrwxrwx 1 root root 43 Nov 25 15:47 /etc/alternatives/javap ->
/usr/lib/jvm/java-7-openjdk-amd64/bin/javap
lrwxrwxrwx 1 root root 53 Nov 25 15:47 /etc/alternatives/javap.1.gz ->
/usr/lib/jvm/java-7-openjdk-amd64/man/man1/javap.1.gz

I don't like this solution though. If I use the /opt/jdk1.7.0/bin/javac
to compile something it still shows the error.

I think something is wrong with the /opt/jdk1.7.0 directory, maybe I
need to reinstall this.

from
Michael

[Darren Wurf]

> I think something is wrong with the /opt/jdk1.7.0 directory, maybe I
> need to reinstall this.
>

Cheap hack: copy /opt/jdk1.7.0 out of your VM :)

[Michael Pope]

I copied /opt/jdk1.7.0 from my broken machine to my VM, so they are
already the same.

I only need /opt/jdk1.7.0 for the mozilla plugin so I've reverted java &
javac back to using openjdk and that works, so I'm going to leave it
like that for now.

from
Mick