Question

我有var x类型ListBuffer[ListBuffer[Int]]我使用函数clone进行克隆并设置为另一个var y，然后使用函数{{1}在这个新的update上更新内容，但是当我检查var y的原始内容时，它与var x相同？为什么是这样？我究竟做错了什么？他们的解决方法是什么？我试图获得ListBuffer的副本，我可以修改，而无需更改初始ListBuffer的原始内容。

Answer 1

clone只制作浅色副本，需要深层复制：

scala> import collection.mutable.ListBuffer
import collection.mutable.ListBuffer

scala> var a = ListBuffer(ListBuffer(1, 2), ListBuffer(3,4))
a: scala.collection.mutable.ListBuffer[scala.collection.mutable.ListBuffer[Int]] = ListBuffer(ListBuffer(1, 2), ListBuffer(3, 4))


scala> var b = a.clone
b: scala.collection.mutable.ListBuffer[scala.collection.mutable.ListBuffer[Int]] = ListBuffer(ListBuffer(1, 2), ListBuffer(3, 4))

scala> b(0)(0) = 100

scala> a
res1: scala.collection.mutable.ListBuffer[scala.collection.mutable.ListBuffer[Int]] = ListBuffer(ListBuffer(100, 2), ListBuffer(3, 4))

scala> b
res2: scala.collection.mutable.ListBuffer[scala.collection.mutable.ListBuffer[Int]] = ListBuffer(ListBuffer(100, 2), ListBuffer(3, 4))

scala> var c = a.clone.map(_.clone)
c: scala.collection.mutable.ListBuffer[scala.collection.mutable.ListBuffer[Int]] = ListBuffer(ListBuffer(100, 2), ListBuffer(3, 4))

scala> c(0)(0) = 1000

scala> c
res3: scala.collection.mutable.ListBuffer[scala.collection.mutable.ListBuffer[Int]] = ListBuffer(ListBuffer(1000, 2), ListBuffer(3, 4))

scala> a
res4: scala.collection.mutable.ListBuffer[scala.collection.mutable.ListBuffer[Int]] = ListBuffer(ListBuffer(100, 2), ListBuffer(3, 4))

克隆ListBuffer不可变问题Scala

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