void reload() throws IOException {
        clear();
        load();
    }
@Test
    public void testReload() throws IOException {
        UserIdMapper mapper = createUserIdMapper(IdStrategy.CASE_INSENSITIVE);
        String user1 = "user1";
        File directory1 = mapper.putIfAbsent(user1, true);
        mapper.reload();
        assertThat(mapper.isMapped(user1), is(true));
        assertThat(mapper.getConvertedUserIds(), hasSize(1));
    }