Scala class to implement two Java Interfaces - how?

Question

I have just started learning Scala and I'm now wondering how I could implement two different Java interfaces with one Scala class? Let's say I have the following interfaces written in Java

public interface EventRecorder {
    public void abstract record(Event event); 
}

public interface TransactionCapable {
    public void abstract commit();
}

But a Scala class can extend only one class at a time. How can I have a Scala class that could fulfill both contracts? Do I have to map those interfaces into traits?

Note, my Scala classes would be used from Java as I am trying to inject new functionality written in Scala into an existing Java application. And the existing framework expects that both interface contracts are fulfilled.

michael.kebe · Accepted Answer · 2016-10-25 05:41:31Z

54

The second interface can be implemented with the with keyword

class ImplementingClass extends EventRecorder with TransactionCapable {
  def record(event: Event) {}
  def commit() {}
}

Further on each subsequent interface is separated with the keyword with.

class Clazz extends InterfaceA
  with InterfaceB
  with InterfaceC {
  //...
}

edited Oct 25, 2016 at 5:41

answered Jun 18, 2010 at 9:39

michael.kebe

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2 Comments

puudeli Over a year ago

Thanks! I actually tried it but IntelliJ spewed out some vague syntax error. I have to try it again and see if the project was setup incorrectly.

Mörkö Over a year ago

Should it be mentioned, that subsequent interfaces are separated with the keyword with? Eg. x extends y with z with q.

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