如何重写Java的ArrayList的addAll（Collection <? extends E> c）Scala中的方法？ 天真的方法不能编译

Question

In MyList I try to override ArrayList 's addAll method (Fig. 2 ). But it does not compile (Fig. 3 ).

How can this be fixed ?

Why is the type incompatible ?

EDIT:

Here is MyList as text:

import java.util
import java.util.ArrayList

class MyList[T] extends ArrayList[T]{
  override def toString()="MyList"

  override def add(o:T)= {
    println ("adding "+o)
    super.add(o)
  }

  override def addAll(c: util.Collection[_ <: T])
  {
    println("addAll"+c)
    super.addAll(c)
  }

}

Answer 1

You forgot a = . It should be:

override def addAll(c: util.Collection[_ <: T])= {
    println("addAll"+c)
    super.addAll(c)
}