Long -> int 타입 변환 질문

@Test
public void findAll() {
    //given
    Member member1 = new Member();
    member1.setName("hi");
    Member member2 = new Member();
    member2.setName("hello");

    //when
    repository.save(member1);
    repository.save(member2);
    List<Member> memberList = repository.findAll();

    //then
    assertThat(memberList.size()).isEqualTo(2);
    assertThat(memberList.get((int) member1.getId())).isEqualTo(member1);
    assertThat(memberList.get((int) (member1.getId() - 0))).isEqualTo(member1);
}

밑에서 두 번째줄 (int) member1.getId()는 컴파일 오류가 발생하는데

맨 밑줄의 (int) (member1.getId() - 0)은 컴파일 오류가 발생하지 않는 이유가 궁금합니다.