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I have java code shown below, how to convert it to scala?
feature.getFeatures()
.stream()
.filter(a -> a.getFeatureName().equals(feature))
.findFirst()
.map(f -> f.Accounts().contains(accountId))
.orElse(true);
Whenever you see filter or find chained with map, think collect or collectFirst
So something like this should work:
feature.getFeatures()
.collectFirst {
case f if f.getFeatureName().equals(feature) =>
f.Accounts().contains(accountId)
}.getOrElse(true)
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Consider the following list(1,1,2,2,3,4,4,5,5) I want to print only 3. Since it is the unique one. Can someone help me with the Scala code.
It's not a Spark question, but this function would do it for Scala
def uniqueElems[T](lst: Seq[T]) = {
lst.groupBy(identity).collect { case v if v._2.length == 1 => v._2.head }
}
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im trying to convert a scala list of eithers, as such:
List(Left(3),Left(4),Left(1),Left(5))
Into a either of a list Either[List[Int],Int] like this?
Left(3,4,1,5)
Only using flatmap, map or fold?
ive been hammering at it for a while now and can simply not make it work
Assumed:
val a = List(Left(1), Left(2), Left(3)) // for example
Then following will return a Left[List[Int]]:
Left(a.map(_.value))
// Left(List(1, 2, 3))
Then you can extract the values out of the list, which I don't thin is generally a good idea.
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Given that match will never be None,
Which style is better or can I improve the first?
val tmp = (cols.find(_(0) == id).get)
SomeClass(tmp(0), tmp(1))
cols.find(_(0) == id) match {
case Some(value)=> SomeClass(value(0), value(1))
case None=> NotFound("Given id not found")
}
Since this a question about style, my answer is that neither of these is the best style. Instead, just keep the value in the Option
val opt: Option[SomeClass] = cols.find(_(0) == id).map(v => SomeClass(v(0), v(1)))
Keep processing/testing inside the Option using foreach/exists etc. until you really need the bare value. There is a very rich set of methods on Option that covers most of the things that are needed.
If the rest of the code is structured well, you will likely find that the value never needs to be extracted in a separate operation.
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I have a trait like this:
trait MyBag[A]{
def add(elem: A): This
}
What is the :This return type? Does this mean the add function returns an instance of MyBag?
This is just the name of a type that is defined somewhere else that you are not showing us. The compiler doesn't speak English, it doesn't care whether a type is named This or Foo or Fgjbgjzdz55437365643w.
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Problem picture
Can anyone tell me what this means:
A = (rs: WrappedResultSet) => throw new IllegalStateException ("The extractor isn't specified yet.")
def fun[A](extractor: WrappedResultSet => A = (rs: WrappedResultSet) => throw new IllegalStateException("The extractor isn't specified yet.")): A
It means that method fun which takes generic type parameter A and a function called extractor of type WrappedResultSet => A. If no value of extractor is passed to fun, then fun uses the default behavior which is to throw IllegalStateException as shown in the code above.
Let me know if it helps!!