如何在方法内引发异常？

Question

def max(xs: List[Int]): Int = if(xs.isEmpty) throw java.util.NoSuchElementException else ...

If xs is empty, an exception should be thrown. However I get an error, since java.util.NoSuchElementException does not match the return type Int

Answer 1

You should try

throw new NoSuchElementException("empty list")

You're trying to throw a class. In Scala, just like in Java, you can only throw an instance of a class and not the class itself. You'd have to use one of NoSuchElementException's constructors.