[soc88]

That's exactly the issue I'm talking about: you can't “enforce” the static type, so different methods get called depending on whether you pass List foo = MyList(...) or MyList foo = MyList(...), which is acceptable for static methods, but a source of bugs when they can be made to look like instance methods.

> Scala has some neat stuff, but it's not Java 8 so I don't see how it's relevant.

Java's default methods are basically Scala's traits (just made a bit more cumbersome to make Java developers feel right at home), so what I said about traits applies to “interfaces with default methods”, too.