Scala Check optional string is null or empty

Question

I am a newbie to Scala and I want to learn how can I add null and empty check on an optional string?

val myString : Option[String]

if (null != myString) {
  myString
    .filter(localStr=> StringUtils.isEmpty(localStr))
    .foreach(localStr=> builder.queryParam("localStr", localStr))
}

Above code works but I want to learn some elegant way of writing same check. Any help is highly appreciated,

thanks

Generally, when using an `Option[T]`, you shouldn't be doing null checks. The exact purpose of an `Option[T]` is to work on a box which may or may not have a value. — Yuval Itzchakov, Sep 02 '16 at 06:57

score 5 · Answer 1 · answered Sep 02 '16 at 07:44

There is a quite convenient way using the Option constructor.

scala> Option("Hello Worlds !")
res: Option[String] = Some(Hello Worlds !)


scala> Option(null)
res: Option[Null] = None

So if you would have list of Strings with possible null values you can use a combination of Option and flatten:

scala> List("Speak", "friend", null, "and", null ,"enter").map(s => Option(s)) .flatten
res: List[String] = List(Speak, friend, and, enter)

Samar · Answer 2 · 2016-09-02T07:12:35.497

4

Pattern matching will help in simplifying your code:

myString match {
case Some(s) if(!s.isEmpty) => s.foreach(localStr=> builder.queryParam("localStr", localStr))
case _ => "No String"
}

edited Sep 02 '16 at 07:12

answered Sep 02 '16 at 07:04

Samar

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You can also use "s.nonEmpty" on Strings, instead of "!s.isEmpty". – Matt Aug 22 '17 at 18:41

score 2 · Answer 3 · answered Sep 02 '16 at 07:20

2

I guess idiomatic way looks like this:

val myString : Option[String] = ...
myString
  .filterNot(StringUtils.isEmpty)
  .foreach(builder.queryParam("localStr", _))

answered Sep 02 '16 at 07:20

Sergii Lagutin

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score 1 · Answer 4 · answered Sep 02 '16 at 07:10

Option[String] can store 2 types of value either Some(String) or None so when u dont need to check for null u just check for None with the help of scala match case as follows

val myString : Option[String] = Some("ss")

 myString match {
   case Some(str)=>str.filter(localStr=> StringUtils.isEmpty(localStr))
    .foreach(localStr=> builder.queryParam("localStr", localStr))
   case None => //do whatever you want while condition failure
 }

Scala Check optional string is null or empty

4 Answers4