java -jar sopc2dts.jar -t dts -i resolving version mismatches

Thanks in advance

I'm getting another computer up and running (been stuck in the old 'vendor_hwselect' due to supporting older projects).

I follow the wiki about DeviceTree. Now when I run the java -jar to get a *.dts I get:

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[janet@localhost sopc2dts]$ java -jar sopc2dts.jar -t dts -i /home/janet/Desktop/cycloneIII_3c120_niosII_standard_sopc.sopcinfo -o /home/janet/Desktop/my.dts

Exception in thread "main" java.lang.UnsupportedClassVersionError: Sopc2DTS : 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: Sopc2DTS. Program will exit.

[janet@localhost sopc2dts]$

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My java and javac versions are:

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[janet@localhost Desktop]$ java -version

java version "1.6.0_24"

OpenJDK Runtime Environment (IcedTea6 1.11.4) (rhel-1.49.1.11.4.el6_3-i386)

OpenJDK Client VM (build 20.0-b12, mixed mode)

[janet@localhost Desktop]$ javac -version

javac 1.7.0_07

[janet@localhost Desktop]$

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I'm assuming that the error is because I have version mismatches?

If so what do I need to do, step-by-step to get the sopc2dts working properly?