CODEWITHSUNDEEP
javascalastream
happy
happy

Reputation: 2628

Scala List of Objects to comma separated String

From java.util.List[CustomObject] I want to remove value and create a comma separated string, tried the below code but got exception

snippet 1

def getVal(a_attribList: List[CustomObject]): String = a_attribList
    .stream()
    .map(new java.util.function.Function[CustomObject, String] {
        override def apply(CustomObject): String = {
            t.getNolumn
        }
    })
    .collect(Collectors.joining(","))

snippet 2

def getVal(a_attribList: List[CustomObject]): String = {
    a_attribList
        .stream()
        .map(a => a.getNolumn)
        .collect(Collectors.joining(","));
}

Exception

type mismatch;
 found   : java.util.function.Function[com.test.dataobjects.CustomObject,String]
 required: java.util.function.Function[_ >: com.test.dataobjects.CustomObject, _ <: R]
            .map(a => a.getNolumn)
                   ^
three errors found

Upvotes: 1

Views: 9249

Answers (3)

Luis Miguel Mej&#237;a Su&#225;rez
Luis Miguel Mej&#237;a Su&#225;rez

Reputation: 22895

As @ValentinCarnu already pointed out the snippets are using scala.collection.immutable.List instead of a java.util.List.
Thus, you only need to map it using an standar scala anonymous function, and then convert it to a String using the mkString method

def getVal(a_attribList: List[CustomObject]): String =
  a_attribList.map(a => a.getNolumn).mkString(",")

Now, if you really have a java List, you can convert it to a Scala list using the JavaConverters package.

import scala.collection.JavaConverters._
def getVal(a_attribList: java.util.List[CustomObject]): String =
  a_attribList.asScala.map(a => a.getNolumn).mkString(",")

Upvotes: 3

Anton Balaniuc
Anton Balaniuc

Reputation: 11739

You can covert it to scala List and do the mapping:

a_attribList.asScala.map(_.getNolumn).mkString(",")

Upvotes: 2

Asya Corbeau
Asya Corbeau

Reputation: 209

Map all your string values and then call 

.mkString(",")

Upvotes: 3

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