[JAVA] Fixed IECore constructor

[likholat]

No description provided.

[ilya-lavrenov]

what does it fix?

[likholat]

@ilya-lavrenov underscore is a special symbol for JNI:

Dynamic linkers resolve entries based on their names. A native method name is concatenated from the following components:

• the prefix Java_

• a mangled fully-qualified class name

• an underscore (_) separator

• a mangled method name

If we use underscore for Java native method name, we must add 1 for c++ function name, or the implementation of this method cannot be found, see:
https://stackoverflow.com/questions/32470463/what-is-the-naming-convention-for-java-native-interface-method-and-module-name/32473938#32473938

Or we shouldn't use underscore for native functions names.