我正在关注 Coursera Scala 类的视频 3.1,但无法让我的 Scala 工作表识别出确实为 Empty 类定义了 contains 方法:
package objsets
abstract class IntSet {
def incl(x:Int): IntSet
def contains(x:Int): Boolean
}
class Empty extends IntSet {
def contains(x: Int): Boolean = false
def incl(x: Int): IntSet = new NonEmpty(x, new Empty, new Empty)
}
class NonEmpty (elem: Int, left: IntSet, right: IntSet) extends IntSet {
def contains(x: Int):Boolean =
if (x < elem) left contains x
else if (x > elem) right contains x
else true
def incl(x:Int):IntSet =
if (x < elem) new NonEmpty(elem, left incl x,right)
else if (x > elem) new NonEmpty(elem, left, right incl x)
else this
}
object Video1 {
val empty = new Empty
empty.contains(2)
}
在对象 Video1 的末尾,当我调用 .contains() 时,我在 Scala IDE 工作表中收到以下错误:
NoSuchMethodError: objsets.Empty.contains(I)Z