### Question:
Iterators { public static int failSafe1() { ConcurrentHashMap<String, Integer> map = new ConcurrentHashMap<>(); map.put("First", 10); map.put("Second", 20); map.put("Third", 30); map.put("Fourth", 40); Iterator<String> iterator = map.keySet() .iterator(); while (iterator.hasNext()) { String key = iterator.next(); map.put("Fifth", 50); } return map.size(); }  static int failFast1(); static int failFast2(); static int failSafe1();  }### Answer:
@Test public void whenFailSafe_ThenDoesNotThrowException() { assertThat(failSafe1()).isGreaterThanOrEqualTo(0); }