jclass cls = env->FindClass("Lnet/minecraft/client/Minecraft;");
jmethodID method = env->GetStaticMethodID(cls, "getMinecraft", "()Lnet/minecraft/client/Minecraft;");
jobject mc = env->CallStaticObjectMethod(cls, method);
// at this point the app crash
jfieldID field = env->GetFieldID(env->GetObjectClass(mc), "thePlayer", "Lnet/minecraft/client/entity/EntityClientPlayerMP;");
jobject thePlayer = env->GetObjectField(mc, field);
jvm->DetachCurrentThread();