java jni demo project refer arrow c-data jni (path: arrow/java/c) JNI docs c api and c++ api is different. c api: const char *str = (*env)->GetStringUTFChars(env, jstr, 0); c++ api: const char *str = env->GetStringUTFChars(jstr, 0); JNI Types and Data Structures Java Native Interface Specification Contents Trail: Java Native Interface: Table of Contents