Forming object of trait from the list of objects of class

Question

My intent is to put the list of Tse objects into Bts object in Java:

    Bts Object should contain List=
    List(Tse(1285927200000,1285928100000,0.0), 
    Tse(1285928100000,1285929000000,1.0), 
    Tse(1285929000000,1285929900000,2.0), 
    Tse(1285929900000,1285930800000,3.0))

I have scala files Bts, Ts and Tse:

Bts.scala

trait Bts extends Ts{
  def start:Long
  def end:Long
  def timezone:TimeZone
}

Ts.scala

Object Ts { //Some methods }
trait Ts extends Iterator[Tse] {
  //Some methods
}

Tse.scala

case class Tse(val start:Long, val end:Long, val value:Option[Double], val elapsed:Long) {
 def this(start: java.lang.Long, end: java.lang.Long, 
 value: java.lang.Double) = {
    this(start, end, Option(value), end-start)
  }
  //Some methods
}

So, in Java code, I want to make Bts object such that it should contain the following:

List(Tse(1285927200000,1285928100000,0.0), 
Tse(1285928100000,1285929000000,1.0), 
Tse(1285929000000,1285929900000,2.0), 
Tse(1285929900000,1285930800000,3.0))

My Java code to do so:

Tse tse1= new Tse(1285927200000L, 1285928100000L, 0.0);

Tse tse2 = new Tse(1285928100000L, 1285929000000L, 1.0);

Tse tse3= new Tse(1285929000000L, 1285929900000L, 2.0);

Tse tse4 = new Tse(1285929900000L, 1285930800000L, 3.0);

List<Tse> entryList = new ArrayList<Tse>();
entryList.add(tse1);
entryList.add(tse2);
entryList.add(tse3);
entryList.add(tse4);

Bts bts= (Bts) entryList; //exception

Tsr$ tsr= Tsr$.MODULE$;
tsr.mcall(bts);

As you see that last line is giving me exception:

Caused by: java.lang.ClassCastException: java.util.ArrayList 
cannot be cast to com.testapp.people.user.Bts

UPDATE:

Tsr.scala

object Tsr {
def mcall(sourceData: Iterator[Tse]) : Bts = { //Other calls}
}

UPDATE:

I tried to create an abstract class in Bts and then tried to access it from Java:

Added the following in Bts.scala:

abstract class Bs(buffer:Iterator[Tse]) extends Bts{
}

From java:

Iterator<Tse> iterator = entryList.iterator();
Bts bts= new Bs(scala.collection.JavaConversions$.MODULE$.
asScalaIterator(iterator)); //exception

Now I am getting compile time error as:

Cannot instantiate the type Bs

Well a Bts is not an ArrayList[Tse]. If you cast that this way, there is no surprise you get a ClassCastException. Could specify more clearly what you want to achieve with the last line? Do you want to create an instance of Bts from Java? Note that traits cannot always be implemented in Java, as per this question. Probably the best would be to provide an abstract class to be used from Java. — 0__
– 0__, Commented Jan 7, 2016 at 11:13
I want to put List of Tse objects i.e. tse1, tse2, tse3 and tse4 into the Bts which is the whole purpose of the story. Later I will call some scala method whose parameter will be this bts object containing the list. Since I didn't found any correct scala way that can put all the tse1, tse2, tse3 and tse4 objects into list and then to bts. So I casted it and got ClassCastException. — sjain
– sjain, Commented Jan 7, 2016 at 11:30
Is it even possible to put the list into Bts from java? I am able to do the same from scala but getting problems here. See my update. The mcall method is taking Iterator[Tse] as argument so I need to pass that from java class which I believe is a list of tse objects in iterator. Also I tried creating an abstract class and used in java without luck. — sjain
– sjain, Commented Jan 7, 2016 at 12:40

bdew · Accepted Answer · 2016-02-01 12:06:53Z

The example you posted is a total mess of weird class names that don't match each other.

I think i understand what you're trying to do, and it's really easy if you make a bit less mess.

Also you should never refer to anything containing $ from your source code unless you really know what you are doing. It's there for the compiler to use.

Scala:

trait Data {
  val foo: Int
  val Bar: Int
}

case class DataCase(foo: Int, Bar: Int) extends Data

object Test {
  def doSomething(it: Iterator[Data]) = {
    for (x <- it) println(x)
  }
}

Java:

import scala.collection.JavaConversions;
import java.util.ArrayList;
import java.util.List;

public class TestJava {
    public static void main(String[] args) {
        List<Data> list = new ArrayList<>();

        list.add(new DataCase(1, 2));
        list.add(new DataCase(3, 4));
        list.add(new DataCase(4, 5));

        Test.doSomething(JavaConversions.asScalaIterator(list.iterator()));
    }
}

Collectives™ on Stack Overflow

Forming object of trait from the list of objects of class

UPDATE:

UPDATE:

1 Answer 1

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

UPDATE:

UPDATE:

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related