OpenICE Execution Ubuntu - Beginner

Hi!
I am glad to have opportunity to communicate with you all.
I am planning to implement testbed as a network of OpenICE devices that all of them are Ubuntu/Debian VMs. I installed JDK 1.7.0-79 as you can see below:

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~/Downloads/OpenICE-0.6.2/bin$ java -version
java version "1.7.0_79"
Java(TM) SE Runtime Environment (build 1.7.0_79-b15)
Java HotSpot(TM) 64-Bit Server VM (build 24.79-b02, mixed mode)

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When I try to execute OpenICE, I face following error, I highly appreciate your help and attention in advance.

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~/Downloads/OpenICE-0.6.2/bin$ ./OpenICE
Exception in thread "main" java.lang.UnsupportedClassVersionError: org/mdpnp/apps/testapp/Main : Unsupported major.minor version 52.0
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:800)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:482)