Java HotSpot Virtual Machine

If I'm calling a void java method while in C++ and I created some local object inside the c++ method (e.g. creating NewStringUTF) after calling CallVoidMethod should I ALWAYS call DeleteLocalRef? What about for a method that returns a value? How do i know when to DeleteLocalRef?

(And if you know, is there a diff. between ReleaseStringChars and DeleteLocalRef? Can i just use DeleteLocalRef?)

Thanks!