[Android] [JNI] Convert jstring to char *

JStringToCharPtr

JNIEXPORT void JNICALL method_name
(JNIEnv *env, jobject obj, jstring jstr)
{
    const char* ch = env->GetStringUTFChars(jstr, 0);

    env->ReleaseStringUTFChars(jstr, ch);
}