if (arg == null) {
        throw new FooException();
      }
    }

    public void noArg() {}

    public void oneArg(String s) {
      checkNotNull(s);
    }

    void packagePrivateOneArg(String s) {
      checkNotNull(s);
    }

    protected void protectedOneArg(String s) {
      checkNotNull(s);
    }

    public void oneNullableArg(@Nullable String s) {}