Get null pointer exception when checking null input

Asked Dec 19 '18 at 15:31

Active Dec 19 '18 at 15:31

Viewed 21 times

I have a class like this.

public class Event {

public Event(String objectName, Integer moduleId, Integer actionId) {

  if (StringUtils.nullOrEmpty(objectName)) {
     throw new IllegalArgumentException("The objectName field is not supplied");
  }
  if (0 > moduleId || null == moduleId) {
     throw new IllegalArgumentException("The moduleId field is invalid");
  }
  if (0 > actionId || null == actionId) {
     throw new IllegalArgumentException("The actionId field is invalid");
  }

  objectName = objectName;
  moduleId = moduleId;
  actionId = actionId;
 }
}

When I test the null value for moduleId and actionId I got the null pointer exception. But it's fine for the objectName. Did I do something wrong?

asked Dec 19 '18 at 15:31

HenlenLee

The order of operation is important – Hovercraft Full Of Eels Dec 19 '18 at 15:32
2

Use `null == moduleId || 0 > moduleId` instead. Otherwise you unbox `moduleId` prior to checking it is null`. – Andy Turner Dec 19 '18 at 15:32
Also, [Yoda conditions](https://en.wikipedia.org/wiki/Yoda_conditions) don't use. The kinds of coding errors they help prevent in other languages don't occur in Java; it just makes the code harder to grok. – Andy Turner Dec 19 '18 at 15:35
It's because you check first if 0 > moduleId and then if its null. Try to replace this conditions and it should works well – Rafał Sokalski Dec 19 '18 at 15:37
Thank you, guys! – HenlenLee Dec 19 '18 at 15:39

Get null pointer exception when checking null input

0 Answers0