Scala：为什么此模式匹配代码会抛出 IndexOutOfBoundsException？

发布于 2024-10-04 00:55:53 字数 1106 浏览 7 评论 0原文

我正在查看一个教程，发现于 http://www.codecommit.com/blog/scala /scala-for-java-refugees-part-4

本教程来自 jan。 2008 年，我明白了，但我正在使用 Scala 2.8.0，如果这有什么区别的话。

class Color(val red:Int, val green:Int, val blue:Int)

case class Red(r:Int) extends Color(r, 0, 0)
case class Green(g:Int) extends Color(0, g, 0)
case class Blue(b:Int) extends Color(0, 0, b)

def printColor(c:Color) = c match {
  case Red(v) => println("Red: " + v)
  case Green(v) => println("Green: " + v)
  case Blue(v) => println("Blue: " + v)

  case col:Color => {
    print("R: " + col.red + ", ")
    print("G: " + col.green + ", ")
    println("B: " + col.blue)
  }

  case null => println("Invalid color")
}

当将其输入解释器时，它会

在线程“main”java.lang.IndexOutOfBoundsException中产生异常在 scala.collection.LinearSeqOptimized$class.apply(LinearSeqOptimized.scala:53) 在 scala.collection.immutable.List.apply(List.scala:45)

加上另外 185 行跟踪，然后解释器退出。

这个错误消息是什么意思，谁能告诉我上面的代码有什么问题？

原文

I was checking out a tutorial, found at
http://www.codecommit.com/blog/scala/scala-for-java-refugees-part-4

This tutorial is from jan. 2008, I see, but I'm using Scala 2.8.0 if that makes a difference.

class Color(val red:Int, val green:Int, val blue:Int)

case class Red(r:Int) extends Color(r, 0, 0)
case class Green(g:Int) extends Color(0, g, 0)
case class Blue(b:Int) extends Color(0, 0, b)

def printColor(c:Color) = c match {
  case Red(v) => println("Red: " + v)
  case Green(v) => println("Green: " + v)
  case Blue(v) => println("Blue: " + v)

  case col:Color => {
    print("R: " + col.red + ", ")
    print("G: " + col.green + ", ")
    println("B: " + col.blue)
  }

  case null => println("Invalid color")
}

When entering this into the interpreter, it produces

Exception in thread "main" java.lang.IndexOutOfBoundsException
at scala.collection.LinearSeqOptimized$class.apply(LinearSeqOptimized.scala:53)
at scala.collection.immutable.List.apply(List.scala:45)

plus another 185 lines of tracing, and the interpreter exits.

What does this error message mean, and can anyone tell me what is wrong with the code above?

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