Question

I am reading scaladocs and just wondering difference between direct assignment and .clone method.

val a=Array(1,2,3,4,5)

case 1:

val b=a

case 2 :

val b=a.clone()

Answer 1

Consider this:

scala> val a=Array(1,2,3,4,5)
a: Array[Int] = Array(1, 2, 3, 4, 5)

scala> val b = a
b: Array[Int] = Array(1, 2, 3, 4, 5)

scala> val c = a.clone()
c: Array[Int] = Array(1, 2, 3, 4, 5)

scala> b(0) = 0

scala> c(1) = 1

scala> a
res2: Array[Int] = Array(0, 2, 3, 4, 5)

scala> b
res3: Array[Int] = Array(0, 2, 3, 4, 5)

scala> c
res4: Array[Int] = Array(1, 1, 3, 4, 5)

As you can see, when you do val b = a, then a and b point to the same object. When the object is changed, the change will be seen by both.

On the other hand, when you clone the array, you produce a new array with the same content. Changing this new array does not change the old one.