Are you sure these functions* start with _Java, and not
Java? Because they look like JNI functions. If you create a native method in Java, then use javah to create a header, that header includes a lot of functions in the following format: Java_<full class name with . replaced by _>_<method name>. For example, if your class is com.coderanch.test.MyClass and it has a native method runTest, then function Java_com_coderanch_test_MyClass_runTest will be created.
That said, these JNI functions shouldn't be called directly but through their native methods in Java. It's a wonder you even managed to properly create the required JNIEnv and jobject / jclass values required to call these JNI functions.