Recent questions tagged Scala

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scala - Creating a method which returns one or two parameters generically

I have a method def foo(num: Int): String Where I call some in some places in my code, and ... more idiomatic scala/functional for this? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - Why do I get conflicting cross-version in sbt on one environment but not another?

I have an sbt project with these dependencies: libraryDependencies ++= Seq( "org.scalatra" %% "scalatra" % ... 6). What's different? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - Explode multiple columns in Spark SQL table

There was a question regarding this issue here: Explode (transpose?) multiple columns in Spark SQL table Suppose that ... code. Any help please. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - How to stop gracefully the actor system for an akka-http server that must be deployed.

I just created my first rest server with akka-http. The problem is that I do not know how to deploy the ... the actor system. Thank you! See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - Spark decimal type precision loss

I'm doing some testing of spark decimal types for currency measures and am seeing some odd precision results when I set the ... ------------+ See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - Creating/accessing dataframe inside the transformation of another dataframe

I'm retrofitting some existing code to use Spark. I've multiple data frames that hold different data sets. ... situation would be very helpful. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - How to apply a function to a column of a Spark DataFrame?

Let's assume that we have a Spark DataFrame df.getClass Class[_ <: org.apache.spark.sql.DataFrame] = class ... number of elements in each row? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - UNRESOLVED DEPENDENCIES installing Deadbolt on Play Framework 2.2.1

I'd like to try Deadbolt. What are the steps to install it on the new Play Framework 2.2.1? What I found is ... Total time: 3 s, completed 12-n See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - Test if implicit conversion is available

I am trying to detect if an implicit conversion exists, and depending on it, to execute some code. For instance : ... Scala? If yes, how? Thanks See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - How to convert keys in a Map to lower case?

I have a map where the key is a String and I need to change every key to lower case before work with ... approach for it? Thanks in advance. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - How to pattern-match against every numeric class in one case?

Suppose I have def foo(x: Any) = x match { case s: String => println(0) case i: Int => println(1) case ... i: Numeric => println("Numeric") } See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - joda DateTime format cause null pointer error in spark RDD functions

The exception message as following User class threw exception: Job aborted due to stage failure: Task 0 in stage ... anybody explain it? Thanks See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala sbt assembly "no main manifest attribute"

I use assembly plugin in sbt to assemble my project. But errors happen when run by "java -jar xx.jar" - " ... in scala sbt. Thanks in advance. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - Is there a way to test at compile-time that a constant is a compile-time constant?

Given how difficult it is to know whether an arithmetic final val expression will be compiled to a compile-time ... / 2 would be possible. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - strange error message: bad symbolic reference. A signature in package.class refers to term apache in package org which is not available

When I tried to compile simple typesafe' akka program (scala 2.10, akka, 2.1.0): scalac -cp "akka ... /useless error message. Thanks, Tomas See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - Handling Doubles in ScalaTest

I have just started using ScalaTest and I am using the following to compare two Doubles in my spec as follows: it ... : def price () : Double See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - why doesn't null.asInstanceOf[Int] throw a NullPointerException?

Since Int "does not conform to" AnyRef, I am not sure why it doesn't throw a NullPointerException according to Scala ... .0.1 and OS windows XP See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - Why wrapping a generic method call with Option defers ClassCastException?

Lets say I have an array like this*: val foo: Any = 1 : Int Option(foo.asInstanceOf[String]) ... doesn't throw a ClassCastException? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - Play 2 - Set header on all responses?

I'm aware from Setting HTTP headers in Play 2.0 (scala)? that you can set response headers on a case-by ... having them added to each response. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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979 views

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scala - NLineInputFormat not working in Spark

What I want is basically to have each element of data consist of 10 lines. However, with the following code, ... ], classOf[Text], c) See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - How does spray.routing.HttpService dispatch requests?

Disclaimer: I have no scala experience for now, so my question is connected with very basics. Consider the ... missing something. Thank you. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - Coalesce duplicate columns in spark dataframe

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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960 views

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scala - How to model an entity with many children in Sorm?

I have a Workspace and Document entities, with the idea that a workspace can contain zero, one, or more documents. My ... : Long, limit: Long) } See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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988 views

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scala - How to read a file from HDFS in map() quickly with Spark

I need to read a different file in every map() ,the file is in HDFS val rdd=sc.parallelize(1 to 10000) ... runs on multiple machines. Thank you! See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - Coalesce duplicate columns in spark dataframe

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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1.2k views

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scala - How do you stop building an Option[Collection] upon reaching the first None?

When building up a collection inside an Option, each attempt to make the next member of the collection might ... idiom to express it. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - Spark Dataset : Example : Unable to generate an encoder issue

New to spark world and trying a dataset example written in scala that I found online On running it through SBT , i keep ... Vic", "age" : "23"} See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - Some questions about difference between call-by-name and 0-arity functions

There are some discussions here about this, but I have some specific questions I wasn't able to find an ... any type representation in scala. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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