ClassCastException thrown when calling .newInstance

I have a program in which I am loading classes dynamically in order to pick which libraries to use at runtime. For some reason, when attempting to instantiate a direct implementer of the interface needing implementation, it throws a ClassCastException. The buggy line can be found here, but reference for below is the process which I use to load the class:

1. The program starts, unaware of the separate .jars (held in another folder).
2. The Collector class loads all the separate .jars' classes and dumps their references in an ArrayList.
3. Another class, Prioritizer, looks in a .json file for the name of what classes to load to do which job, referring to the interface as a caster. This class then queries the Collector class for the object reference.
4. The main class calls on the Prioritizer to find the right class reference for an implementation of LanguageDetail, which it then attempts to cast, then instantiate, and call a method from.

In step four, however, the cast fails and an exception is thrown.

The offending line is this:

Collector.prioritizer.get(LanguageDetail.class).newInstance().reportLanguageDetails();

However, this throws the following exception:

java.lang.ClassCastException: com.VTC.laura.test.TestLangDetails cannot be cast to com.VTC.langlib.data.LanguageDetail
    at com.VTC.laura.core.Main.main(Main.java:23)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at org.eclipse.jdt.internal.jarinjarloader.JarRsrcLoader.main(JarRsrcLoader.java:58)

Even though TestLangDetails is a direct implementation of LanguageDetail.

What am I doing wrong to cause this error, and how can I fix it?