Avoid checking null value of intermediates objects

Question

We have all seen that kind of code

if (myObject!= null 
  && myObject.mySubObject() != null
  && myObject.mySubObject().getSpecificValue() != null
  && !myObject.mySubObject().getSpecificValue().isEmpty()
) {
     ......
}

How could I write this the clean way ?

Unfortunately, this **is** the "clean way". Welcome to Java! — Jordan, Jan 29 '20 at 15:58
[Optionals](https://www.tutorialspoint.com/java8/java8_optional_class.htm) are an alternative, but they need training to handle right, otherwise they are as messy as this. However, as @Jordan already noticed, this kinda is the way you do it in java... — gkhaos, Jan 29 '20 at 15:59
Does this answer your question? [Java "?" Operator for checking null - What is it? (Not Ternary!)](https://stackoverflow.com/questions/4390141/java-operator-for-checking-null-what-is-it-not-ternary) — Orace, Jan 29 '20 at 16:00
Does this answer your question? https://stackoverflow.com/questions/27074474/is-there-a-operator-for-java-to-perform-null-pointer-checking — Orace, Jan 29 '20 at 16:04
Agreed with @Jordan, also NPE can come handy in cases where the target object are too deep level. just Use try catch block for `NullPointerException` If in `catch`, treat as `else`, otherwise, proceed using the target object in `try block` as `if block`. It's not worth mentioning this as answer, so putting in comments only `try { Object o = myObject.mySubObject().getSpecificValue(); // use o further } catch(NullPointerException npe){ // else logic can come here; }` — miiiii, Jan 29 '20 at 16:06
@Orace I hoped a nicest way would exist, what do you mean by pure / time consuming ? — Seb, Jan 29 '20 at 16:19
@miiiii Don’t ever catch NullPointerException, ever, under any circumstances. NullPointerException exists to expose programmer errors. Catching it prevents mistakes from being detected. — VGR, Jan 29 '20 at 17:29
@VGR I know. that's why said in comments that it's not good to use NPE hence not considering it as answer. Just mentioned as work around (but very bad alternative). — miiiii, Jan 29 '20 at 18:55

score 6 · Answer 1 · edited Jan 29 '20 at 16:10

6

You can do chaining with Optional:

Optional.ofNullable(myObject)
  .map(o -> o.mySubObject())
  .map(so -> so.getSpecificValue())
  .map(sv -> sv.isEmpty())
  .orElse(false)

Or with method references even shorter (does the same):

Optional.ofNullable(myObject)
  .map(Foo::mySubObject)
  .map(Bar::getSpecificValue)
  .map(Baz::isEmpty)
  .orElse(false)

where Foo, Bar and Baz are the names of the respective classes.

edited Jan 29 '20 at 16:10

Zabuzard

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answered Jan 29 '20 at 16:03

Iskuskov Alexander

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1

Neat way of using Optionals! – gkhaos Jan 29 '20 at 16:06
1

You can also use method references. – Zabuzard Jan 29 '20 at 16:09
Just wandering, won't it create NPE on `so.getSpecificValue()` if `o.mySubObject()` returned `null`. – miiiii Jan 29 '20 at 16:10
1

@miiiii No, because `Optional#map` will only continue if the Optional is present, i.e. not empty. So this is ensured by starting with `Optional.ofNullable`. That is the whole point of the `map` method in `Optional`. – Zabuzard Jan 29 '20 at 16:11
I like the way but it's still very long and not "clear", I mean it's not obvious that you're trying to check specificValue existence – Seb Jan 29 '20 at 16:14
1

@Zabuza just wrote a code in IDE and ran as I was not convinced yet. But You're right. It works as expected. I wasn't aware of this. Thanks. I wish could give upvote for your explanation. :) – miiiii Jan 29 '20 at 16:22
That is probably the best general purpose solution for this situation that exists in Java. I personally like it, have a better suggestion? What kind of syntax would you like to have? I can not really come up with something more compact/clean. – Zabuzard Jan 29 '20 at 16:22
I mean, you could always just create a little helper method to do exactly that `private static boolean doesBazExist(Foo foo)` if you really have to do this more than once. – Zabuzard Jan 29 '20 at 16:24
1

Yup. Agreed. I must say, the way Java has implemented functional programming paradigm is much nicer than traditional Functional Languages I've explored so far. Nice to talk to you. :) – miiiii Jan 29 '20 at 16:25
a scope?.subobject?.specificValue would be nice, what do you think ? – Seb Jan 29 '20 at 16:34
I see. That would be a feature integrated into the language level. Like in languages like Kotlin. So far Java does not offer anything in that direction, on a language level. – Zabuzard Jan 29 '20 at 16:35

score 1 · Answer 2 · edited Jan 29 '20 at 16:35

1

If you are using someone else's code then you're really stuck handling for a possible null. On the other hand, if you have control over the code base then never return a null object, and make that a rule across your entire application.

This may sound bad at first but I have developed several enterprise-level applications and this is a very effective way to make the code consistent and much more readable.

So, now, this

if (myString != null && !myString.isEmpty()) {

becomes simply

if (!myString.isEmpty()) {

In lue of that option use the new Optional feature in J8 as it is intended for that purpose.

edited Jan 29 '20 at 16:35

Zabuzard

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answered Jan 29 '20 at 16:22

AstarAndy

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This is the correct answer: Do not treat null as a normal value. Most of the time, null is not needed in complex objects, especially collection properties. – VGR Jan 29 '20 at 17:32

Avoid checking null value of intermediates objects

2 Answers2