Q: java.lang.UnsupportedClassVersionError: com/ubikingenierie/jmeter/plugin/hls/result/HLSSampleResultConverter : Unsupported major.minor version 51.0 Running Apache JMeter 2.13 with Java 6 (1.6.0_65) and UbikLoadPack HLS plugin 
I get this exception at startup:
 2016/02/15 15:11:45 ERROR - jmeter.JMeter: Uncaught exception:  java.lang.UnsupportedClassVersionError: com/ubikingenierie/jmeter/plugin/hls/result/HLSSampleResultConverter : Unsupported major.minor version 51.0
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClassCond(ClassLoader.java:637)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:621)
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
    at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:171)
    at org.apache.jmeter.save.SaveService.registerConverter(SaveService.java:297)
    at org.apache.jmeter.save.SaveService.initProps(SaveService.java:250)
    at org.apache.jmeter.save.SaveService.<clinit>(SaveService.java:191)
    at org.apache.jmeter.gui.action.Load.loadProjectFile(Load.java:130)
    at org.apache.jmeter.gui.action.Load.loadProjectFile(Load.java:102)
    at org.apache.jmeter.gui.action.LoadRecentProject.doAction(LoadRecentProject.java:68)
    at org.apache.jmeter.gui.action.ActionRouter.performAction(ActionRouter.java:81)
    at org.apache.jmeter.gui.action.ActionRouter.access$000(ActionRouter.java:40)
    at org.apache.jmeter.gui.action.ActionRouter$1.run(ActionRouter.java:63)
    at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:715)
    at java.awt.EventQueue.access$400(EventQueue.java:82)
    at java.awt.EventQueue$2.run(EventQueue.java:676)
    at java.awt.EventQueue$2.run(EventQueue.java:674)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:86)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:685)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:296)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:211)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:201)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:196)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:188)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)


A: Not being able to run your own stuff might be very frustrating. It is due to Java version mismatch i.e. you're trying to run code compiled with higher version of Java on lesser version of runtime.  
Remember to always use the latest version of JMeter and the latest version of Java (choose 64-bit Server JRE or JDK for your operating system). 
You're also welcome to check out 9 Easy Solutions for a JMeter Load Test "Out of Memory" Failure guide for other recommendations on tweaking JMeter for maximum performance. 

A: Plugin requires Java 7 to run even with Apache JMeter 2.13.
So ensure you use a Java 7 or Java 8.
Besides, if using Java 8, ensure you use a JMeter 2.12 or superior as JMeter is compatible with Java 8 only starting from this version.
