scala> import scala.io.Source
import scala.io.Sourcescala> val lines=Source.fromFile("F:/ziyuan_badou/file.txt").getLines().toList
lines: List[String] = List("With the development of civilization, it is the chil
dren's duty to study in school since they were small. As the young kids, it is t
heir nature to hang out for fun. ", "", "While for them, most of the time have b
een limited in the class. So they feel frustrated and don't have much passion tostudy. It is of great importance to develop ", "", "interest. The first thing i
s to broaden vision. The students can read travel books or watch tourist show, f
or anyone who cannot resist the charm of beautiful scenery ", "", and delicious
food. The second thing is taking the right attitude to exams. Never giving too m
uch pressure on getting high marks. The only thing we should do is to enjoy gain
ing knowledge.)

scala> lines.map(x=>x.split(" ")).flatten.map(x=>(x,1)).groupBy(x=>x._1).map(x=>
(x._1,x._2.map(x=>x._2).sum)).toList.sortBy(x=>x._2).reverse

res0: List[(String, Int)] = List((the,7), (to,7), (is,6), (of,4), (The,4), (thin
g,3), (for,3), ("",3), (and,2), (much,2), (they,2), (it,2), (have,2), (in,2), (o
nly,1), (right,1), (show,,1), (exams.,1), (high,1), (since,1), (study,1), (study
.,1), (great,1), (we,1), (interest.,1), (develop,1), (As,1), (passion,1), (were,
1), (time,1), (them,,1), (children's,1), (development,1), (knowledge.,1), (It,1)
, (anyone,1), (Never,1), (nature,1), (enjoy,1), (first,1), (taking,1), (frustrat
ed,1), (books,1), (delicious,1), (So,1), (their,1), (resist,1), (should,1), (sma
ll.,1), (gaining,1), (While,1), (who,1), (on,1), (can,1), (been,1), (second,1),
(travel,1), (most,1), (scenery,1), (getting,1), (attitude,1), (cannot,1), (civil
ization,,1), (broaden,1), (out,1), (food.,1), (don't,1), (importance,1), (kid...