How to use less than < or greater > than in kotlin [duplicate]

Question

How to use less than (<) or greater than (>) operator in kotlin?

I have checked comparedTo(other: Int?) function, but it only returns Int?.

class Adapter{ private var mNewsCategories: List<NewsCategory>? = null //...... val isAnything= this.mNewsCategories?.size?.compareTo(0)) //...... }

The val isAnything returns another Int?. Actually, I need a Boolean variable.

Thanks in advance

@OliverCharlesworth Don't know, but I wonder how adding > 0 would work semantically with null values, since that's how I understood your suggestion. — Marko Topolnik
– Marko Topolnik, Commented Feb 18, 2018 at 12:11

s1m0nw1 · Accepted Answer · 2018-02-18 20:56:34Z

9

It’s not possible to use > on nullable types. If you consider null to map to the size 0, i.e. empty size, you can do:

val isAnything = (this.mNewsCategories?.size? ?: 0) > 0

While this will fix your problem, you should consider using isNotEmpty instead:

val isAnything = this.mNewsCategories?.isNotEmpty() ?: false

The Elvis Operator is explained here.

answered Feb 18, 2018 at 12:01

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4 Comments

Thanks for the precious answer. Can you explain elvis operator do, it will help lot of others .

Though, when checking for empty lists using isNotEmpty is probably easier than comparing to 0

That's probably true