Java 8 nested null check and access first element

Question

How can I convert the below legacy java code to use Optional :

if (outer != null
        && outer.getInnerMethod() != null
        && outer.getInnerMethod().isAllowed()) {
   Obj value = outer.getInnerMethod().getSomethingElse();
}

Using something like Optional.ofNullable took me till here -

Optional.ofNullable(Outer.getOuter)
        .map(Outer::getInnerMethod)
        .map(SomethingElse::isAllowed)
        .ifPresent(.. );

But ifPresent will not have access to the outer object. What would be the cleanest way to transform something like this ?

Its kind of a 6 line unit test candidate to see what will happen. — Antoniossss
– Antoniossss, Commented May 6, 2020 at 7:25
You are mapping to isAllowed(), which yields an Optional<Boolean>. You want to use filter instead. — MC Emperor
– MC Emperor, Commented May 6, 2020 at 7:33

Kunal Vohra · Accepted Answer · 2020-05-06 07:33:17Z

2

Do this

Optional.ofNullable(Outer.getOuter)
        .filter(outer -> ::Objects.nonNull(outer.getInnerMethod()))
        .filter(SomethingElse::isAllowed)
        .map (.. ); //or whatever operation you want to do here

answered May 6, 2020 at 7:33

Kunal Vohra

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Comments

Lino · Accepted Answer · 2020-05-06 07:33:55Z

1

Use filter instead of map. From the java doc

If a value is present, and the value matches the given predicate, return an Optional describing the value, otherwise return an empty Optional.

Optional<Obj> optional = Optional.ofNullable(Outer.getOuter)
    .map(Outer::getInnerMethod)
    .filter(SomethingElse::isAllowed)
    .map(SomethingElse::getSomethingElse);

answered May 6, 2020 at 7:33

Lino

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Comments

Under_Koen · Accepted Answer · 2020-05-06 17:04:10Z

1

Instead of using map to chech if it's allowed use filter(e -> e.isAllowed()) this will filter out anything that isn't allowed.

edited May 6, 2020 at 17:04

answered May 6, 2020 at 7:34

Under_Koen

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