Scala - 打印数组
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Scala - printing arrays
提问by I82Much
It seems like the support for printing arrays is somewhat lacking in Scala. If you print one, you get the default garbage you'd get in Java:
Scala 似乎缺乏对打印数组的支持。如果你打印一个，你会得到你在 Java 中得到的默认垃圾：
scala> val array = Array.fill(2,2)(0)
array: Array[Array[Int]] = Array(Array(0, 0), Array(0, 0))
scala> println(array)
[[I@d2f01d
Furthermore, you cannot use the Java toString/deepToString methods from the java.util.Arrays class: (or at least I cannot figure it out)
此外，您不能使用 java.util.Arrays 类中的 Java toString/deepToString 方法：（或者至少我无法弄清楚）
scala> println(java.util.Arrays.deepToString(array))
<console>:7: error: type mismatch;
found : Array[Array[Int]]
required: Array[java.lang.Object]
println(java.util.Arrays.deepToString(array))
The best solution I could find for printing a 2D array is to do the following:
我能找到的打印二维数组的最佳解决方案是执行以下操作：
scala> println(array.map(_.mkString(" ")).mkString("\n"))
0 0
0 0
Is there a more idiomatic way of doing this?
有没有更惯用的方法来做到这一点？
回答by Arjan Blokzijl
In Scala 2.8, you can use the deepmethod defined on Array, that returns an IndexedSeq cointaining all of the (possibly nested) elements of this array, and call mkString on that:
在 Scala 2.8 中，您可以使用deep在 Array 上定义的方法，该方法返回一个包含该数组所有（可能嵌套）元素的 IndexedSeq，并在其上调用 mkString：
scala> val array = Array.fill(2,2)(0)
array: Array[Array[Int]] = Array(Array(0, 0), Array(0, 0))
scala> println(array.deep.mkString("\n"))
Array(0, 0)
Array(0, 0)
The IndexedSeq returned does have a stringprefix 'Array' by default, so I'm not sure whether this gives precisely what you wanted.
默认情况下，返回的 IndexedSeq 确实有一个 stringprefix 'Array'，所以我不确定这是否正是您想要的。
回答by Eastsun
How about this:
这个怎么样：
scala> val array = Array.fill(2,2)(0)
array: Array[Array[Int]] = Array(Array(0, 0), Array(0, 0))
scala> import scala.runtime.ScalaRunTime._
import scala.runtime.ScalaRunTime._
scala> val str = stringOf(array)
str: String =
Array(Array(0, 0), Array(0, 0))
回答by akuriako
Adding little more to Arjan's answer - you can use the mkString method to print and even specify the separator between elements. For instance :
为 Arjan 的答案添加更多内容 - 您可以使用 mkString 方法打印甚至指定元素之间的分隔符。例如 ：
val a = Array(1, 7, 2, 9)
a.mkString(" and ")
// "1 and 7 and 2 and 9"
a.mkString("<", ",", ">") //mkString(start: String, sep: String, end: String)
// "<1,7,2,9>"
回答by Noha Elprince
Try simply this:
试试这个：
// create an array
val array1 = Array(1,2,3)
// print an array elements seperated by comma
println(array1.mkString(","))
// print an array elements seperated by a line
println(array1.mkString("\n"))
// create a function
def printArray[k](a:Array[k])= println(a.mkString(","))
printArray(array1)
回答by rupert160
I rather like this one:
我比较喜欢这个：
Array(1, 7, 2, 9).foreach(println)
回答by David Weber
You can get neat formatting of Array[Array[Somethings]] with custom separators for the inner as well as the outer array follows:
您可以使用内部和外部数组的自定义分隔符获得 Array[Array[Somethings]] 的整洁格式，如下所示：
def arrayToString(a: Array[Array[Int]]) : String = {
val str = for (l <- a) yield l.mkString("{", ",", "}")
str.mkString("{",",\n","}")
}
val foo = Array.fill(2,2)(0)
println(arrayToString(foo))
This results in:
这导致：
{{0,0},
{0,0}}
回答by Enrico Susatyo
The "functional programming" way to do this (as far as I concern) is:
执行此操作的“函数式编程”方式（就我而言）是：
scala> array foreach{case a => a foreach {b => print(b.toString + " ")}; print('\n')}
0 0
0 0
Or if you don't really care about the spacing:
或者，如果您真的不关心间距：
scala> array foreach{a => a foreach println}
0
0
0
0
IMHO, functional programming can get a little messy, if it takes too long to make this, I'd say just go with the imperative way.
恕我直言，函数式编程可能会变得有点混乱，如果需要很长时间才能做到这一点，我会说只是采用命令式方式。
