如何在 Scala 中打印任何内容的列表？
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How do I print a List of anything in Scala?
提问by deltanovember
At the moment I have a method that prints Ints
目前我有一个打印 Ints 的方法
def printList(args: List[Int]): Unit = {
args.foreach(println)
}
How do I modify this so it is flexible enough to print a list of anything?
我如何修改它以便它足够灵活以打印任何内容的列表？
回答by Kevin Wright
You don't need a dedicated method, the required functionality is already right there in the collection classes:
您不需要专用方法，所需的功能已经在集合类中：
println(myList mkString "\n")
mkStringhas two forms, so for a List("a", "b", "c"):
mkString有两种形式，所以对于 a List("a", "b", "c")：
myList.mkString("[",",","]") //returns "[a,b,c]"
myList.mkString(" - ") // returns "a - b - c"
//or the same, using infix notation
myList mkString ","
My example just used \nas the separator and passed the resulting string to println
我的例子只是用作\n分隔符并将结果字符串传递给println
回答by Alexey Romanov
Since printlnworks on anything:
由于println适用于任何事情：
def printList(args: List[_]): Unit = {
args.foreach(println)
}
Or even better, so you aren't limited to Lists:
甚至更好，因此您不仅限于Lists：
def printList(args: TraversableOnce[_]): Unit = {
args.foreach(println)
}
回答by Thomas Lockney
You just need to make the method generic
你只需要使方法通用
def printList[A](args: List[A]): Unit = {
args.foreach(println)
}
回答by IttayD
def printList[T](args: List[T]) = args.foreach(println)
回答by Jan Clemens Stoffregen
Or a recursive version to practise :)
或者一个递归版本来练习:)
1 - Declare your List
1 - 声明你的清单
val myCharList: List[Char] = List('(',')','(',')')
2 - Define your method
2 - 定义你的方法
def printList( chars: List[Char] ): Boolean = {
if ( chars.isEmpty ) true //every item of the list has been printed
else {
println( chars.head )
printList( chars.tail )
}
}
3 - Call the method
3 - 调用方法
printList( myCharList )
Output:
输出：
(
)
(
)
