While there is documentation regarding turning a jstring to a native string (string nativeString = env->GetStringUTFChars(jStringVariable, NULL);
jstring
string nativeString = env->GetStringUTFChars(jStringVariable, NULL);
If you just want to use it in if(..) statement, this is working for me without conversion:
if (jboolean == true) { return true; } else { return false; }