[Solved]-How can I select a non-sequential subset elements from an array using Scala and Spark?-scala

You can use map on indices, which maps each element to a new element based on a mapping lambda. Note that on Array, you get an element at an index with the apply method:

indices.map(index => A.apply(index))

You can leave off apply:

indices.map(index => A(index))

You can also use the underscore syntax:

indices.map(A(_))

When you're in a situation like this, you can even leave off the underscore:

indices.map(A)

And you can use the alternate space syntax:

indices map A

You were trying to use foreach, which returns Unit, and is only used for side effects. For example:

indices.foreach(index => println(A(index)))
indices.map(A).foreach(println)
indices map A foreach println