Multiple variable loop in scala

Question

I wants to iterate two variable in loop and populate the map.Java code looks like below.

for (int i = 0, j = 0; i < header.size(); i++, j++)
{
  map.put(header.get(i), cols.get(j));
}

How can we achieve this in Scala? Please can anyone help on this? Help appreciated.

Why do you need two variables here? Variables i and j always have the same value, haven't they? So why don't use i instead of j? If your real code is more complicated - show us some better example. — SergGr
– SergGr, Commented Nov 27, 2017 at 4:25

chengpohi · Accepted Answer · 2017-11-27 02:17:35Z

5

In Scala, you can use zip to do this, like:

header.zip(cols).toMap

answered Nov 27, 2017 at 2:17

chengpohi

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2 Comments

user1734980 Over a year ago

When i added this line of code in programmer it doesn't iterates more than a single record.

chengpohi Over a year ago

@user1734980, I think you can paste a runnable code for this. if your header or cols not Scala Collection, maybe you need to convert it to Scala collection.

prayagupadhyay · Accepted Answer · 2017-11-27 02:27:12Z

1

One way is map over your headers along with the index of each entry and get the col for the same index and create a map.

Given,

scala> val headers = Seq("h1", "h2", "h3", "h4")
headers: Seq[String] = List(h1, h2, h3, h4)

scala> val cols = Seq("c1", "c2", "c3")
cols: Seq[String] = List(c1, c2, c3)

map on headers cols.lift(i) is safe way when headers.size > cols.size

scala> headers.zipWithIndex.map{case (h, i) => h -> cols.lift(i).getOrElse("")}.toMap
res50: scala.collection.immutable.Map[String,String] = Map(h1 -> c1, h2 -> c2, h3 -> c3, h4 -> "")

If headers.size == cols.size or if you don't want header which does not have equvalent col, you can use list.zip(anotherList),

scala> headers.zip(cols)
res52: Seq[(String, String)] = List((h1,c1), (h2,c2), (h3,c3))

edited Nov 27, 2017 at 2:27

answered Nov 27, 2017 at 2:21

prayagupadhyay

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Comments

Aluan Haddad · Accepted Answer · 2017-11-27 02:32:46Z

1

I was going to suggest

val map = (0 until header.size) map { n => header.get(n) -> header.col(n) } toMap

As a fairly naive translation.

This assumes that header is just an arbitrary object with a few defs, not a proper collection.

answered Nov 27, 2017 at 2:32

Aluan Haddad

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