Scala：将元素附加到数组的最佳方法是什么？
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/7500081/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Scala: what is the best way to append an element to an Array?
提问by Gregor Scheidt
Say I have an Array[Int]like
说我Array[Int]喜欢
val array = Array( 1, 2, 3 )
Now I would like to append an element to the array, say the value 4, as in the following example:
现在我想将一个元素附加到数组中，比如 value 4，如下例所示：
val array2 = array + 4 // will not compile
I can of course use System.arraycopy()and do this on my own, but there must be a Scala library function for this, which I simply could not find. Thanks for any pointers!
我当然可以System.arraycopy()自己使用和执行此操作，但是必须有一个 Scala 库函数，我根本找不到。感谢您的任何指点！
Notes:
笔记：
I am aware that I can append another Array of elements, like in the following line, but that seems too round-about:
val array2b = array ++ Array( 4 ) // this worksI am aware of the advantages and drawbacks of List vs Array and here I am for various reasons specifically interested in extending an Array.
我知道我可以附加另一个元素数组，如下行所示，但这似乎太迂回了：
val array2b = array ++ Array( 4 ) // this works我知道 List 与 Array 的优缺点，出于各种原因，我对扩展数组特别感兴趣。
Edit 1
编辑 1
Thanks for the answers pointing to the :+operator method. This is what I was looking for. Unfortunately, it is rather slower than a custom append() method implementation using arraycopy-- about two to three times slower. Looking at the implementation in SeqLike[], a builder is created, then the array is added to it, then the append is done via the builder, then the builder is rendered. Not a good implementation for arrays. I did a quick benchmark comparing the two methods, looking at the fastest time out of ten cycles. Doing 10 million repetitions of a single-item append to an 8-element array instance of some class Footakes 3.1 sec with :+and 1.7 sec with a simple append()method that uses System.arraycopy();doing 10 million single-item append repetitions on 8-element arrays of Long takes 2.1 sec with :+and 0.78 sec with the simple append()method. Wonder if this couldn't be fixed in the library with a custom implementation for Array?
感谢您提供指向:+操作符方法的答案。这就是我一直在寻找的。不幸的是，它比使用自定义 append() 方法实现arraycopy要慢——大约慢两到三倍。查看 中的实现SeqLike[]，创建了一个构建器，然后将数组添加到其中，然后通过构建器完成追加，然后呈现构建器。不是一个好的数组实现。我做了一个比较两种方法的快速基准测试，查看十个周期中最快的时间。将单个项目附加到某个类的 8 元素数组实例的 1000 万次重复Foo需要 3.1 秒，:+使用一个简单的append()方法需要1.7 秒System.arraycopy();在 Long 的 8 元素数组上执行 1000 万次单项追加重复需要 2.1 秒，:+使用简单append()方法需要0.78 秒。想知道这是否无法通过自定义实现在库中修复Array？
Edit 2
编辑 2
For what it's worth, I filed a ticket: https://issues.scala-lang.org/browse/SI-5017
对于它的价值，我提交了一张票：https: //issues.scala-lang.org/browse/SI-5017
回答by tenshi
You can use :+to append element to array and +:to prepend it:
您可以使用:+将元素附加到数组并添加+:它：
0 +: array :+ 4
should produce:
应该产生：
res3: Array[Int] = Array(0, 1, 2, 3, 4)
It's the same as with any other implementation of Seq.
它与Seq.
回答by Landei
val array2 = array :+ 4
//Array(1, 2, 3, 4)
Works also "reversed":
作品也“颠倒”：
val array2 = 4 +: array
Array(4, 1, 2, 3)
There is also an "in-place" version:
还有一个“就地”版本：
var array = Array( 1, 2, 3 )
array +:= 4
//Array(4, 1, 2, 3)
array :+= 0
//Array(4, 1, 2, 3, 0)
回答by Nicolas
The easiest might be:
最简单的可能是：
Array(1, 2, 3) :+ 4
Actually, Array can be implcitly transformed in a WrappedArray
实际上，Array 可以隐式转换为 WrappedArray
