Question

I’m currently working on a port of a jEdit plugin to write all code in Scala. However Im forced at a certain point to implement my own Comparator.

My simplified code is as follows:

class compare extends MiscUtilities.Compare {
  def compare(obj1: AnyRef, obj2: AnyRef): Int = 1
}

The MiscUtilities.Compare has the following signature when looking from IntelliJ

public static interface Compare extends java.util.Comparator {        
    int compare(java.lang.Object o, java.lang.Object o1);
}

However when im trying to compile my class I get a error saying:

error: class compare needs to be abstract, since method compare in trait Comparator of type (x$1: T,x$2: T)Int is not defined
class compare extends MiscUtilities.Compare {

I have also tried with Any and java.lang.Object as types, but no luck so far.

Help is very much appreciated:)

Regards Stefan

Answer 1

It may be impossible. If this is wrong, I would like to know.

EDIT: But you can do this instead:

// CompareImpl.java
abstract class CompareImpl implements MiscUtilities.Compare {
  public int compare(Object o, Object o1) {
    return doCompare(o, o1);
  }

  public abstract int doCompare(Object o, Object o1);
}

// MyCompare.scala
object MyCompare extends CompareImpl {
  def doCompare(a: AnyRef, b: AnyRef) = 0
}

So you still have to write some Java, but only one trivial class for each interface like MiscUtilities.Compare.