Scala学习(九)练习

1. 编写一小段Scala代码，将某个文件中的行倒转顺序，将最后一行作为第一行,依此类推

程序代码:

1. import scala.io.Source
2. import java.io.PrintWriter
3.  
4. object ReverseLines extends App {
5.   val filename="File.txt"
6.   val RefileName="ReverseFile.txt"
7.  
8.   val source=Source.fromFile("src\\"+filename)
9.   lazy val ReSource=Source.fromFile("src\\"+RefileName)
10.   lazy val pw = new PrintWriter("src\\"+RefileName)
11.  
12.   val linesIterator=source.getLines()
13.   val linesRecord=linesIterator.toArray
14.   val reverseRecord=linesRecord.reverse
15.  
16.   reverseRecord.foreach {
17.     line =>pw.write(line+"\n")
18.   }
19.   pw.close()
20.  
21.   println(filename+"文件内容如下:")
22.   linesRecord.foreach (line=>println(line))
23.  
24.   println(RefileName+"文件内容如下:")
25.   ReSource.getLines().foreach(line=>println(line))
26. }

运行结果:

File.txt文件内容如下:

Inc said they plan to form a venture to manage the money market

borrowing and investment activities of both companies.

BP North America is a subsidiary of British Petroleum Co

Plc <BP>, which also owns a 55 pct interest in Standard Oil.

The venture will be called BP/Standard Financial Trading

and will be operated by Standard Oil under the oversight of a

joint management committee.

ReverseFile.txt文件内容如下:

joint management committee.

and will be operated by Standard Oil under the oversight of a

The venture will be called BP/Standard Financial Trading

Plc <BP>, which also owns a 55 pct interest in Standard Oil.

BP North America is a subsidiary of British Petroleum Co

borrowing and investment activities of both companies.

Inc said they plan to form a venture to manage the money market

2. 编写Scala程序，从一个带有制表符的文件读取内容，将每个制表符替换成一组空格，使得制表符隔开的n列仍然保持纵向对齐，并将结果写入同一个文件

程序代码:

1. object TabSpace extends App{
2.   val FileName="TabSpace"
3.   val path="src\\"+FileName+".txt"
4.   val linesIterator=Source.fromFile(path).getLines()
5.   lazy val TabIterator=Source.fromFile(path).getLines()
6.   val linesRecord=linesIterator.toArray
7.   lazy val pw=new PrintWriter(path)
8.   println(FileName+"文件内容如下:")
9.   linesRecord.foreach(println)
10.   linesRecord.foreach {
11.     line =>pw.write(line.replaceAll("\t", "")+"\n")
12.   }
13.   pw.close
14.   println("替换后"+FileName+"文件内容如下:")
15.   TabIterator.foreach(println)
16.  
17. }

运行结果:

TabSpace文件内容如下:

Inc    said    they    plan    to    form    a    venture    to    manage    the    money    market

Inc    ssss    adfs    sdjf    sd    dskl    s    jdakwus    sd    sdskkl    sds    sdsds    djslkl

Inc    said    they    plan    to    form    a    venture    to    manage    the    money    market

Inc    ssss    adfs    sdjf    sd    dskl    s    jdakwus    sd    sdskkl    sds    sdsds    djslkl

Inc    said    they    plan    to    form    a    venture    to    manage    the    money    market

替换后TabSpace文件内容如下:

Inc said they plan to form a venture to manage the money market

Inc ssss adfs sdjf sd dskl s jdakwus sd sdskkl sds sdsds djslkl

Inc said they plan to form a venture to manage the money market

Inc ssss adfs sdjf sd dskl s jdakwus sd sdskkl sds sdsds djslkl

Inc said they plan to form a venture to manage the money market

3. 编写一小段Scala代码，从一个文件读取内容并把所有字符数大于12的单词打印到控制台。如果你能用单行代码完成会有额外奖励

程序代码：

1. object CheckString extends App{
2.   val FileName="CheckString"
3.   val path="src\\"+FileName+".txt"
4.   println(FileName+"文件中长度大于12的字符串为:")
5.   io.Source.fromFile(path).mkString.split("\\s+").foreach (str => if(str.length()>12) println(str))
6. }

运行结果：

CheckString文件中长度大于12的字符串为:

Incsaidtheyplan

jdakwussdsdskkl

managethemoneymarket

dsklsjdakwussdsdskkl

venturetomanagethe

4. 编写Scala程序，从包含浮点数的文本文件读取内容，打印出文件中所有浮点数之和，平均值，最大值和最小值

程序代码：

1. object ReadNumber extends App{
2.   val pattern="(\\d+[.]\\d+)".r
3.   val pattern1="^\\d+(\\.\\d+)?".r
4.   val pattern2="[0-9]+(\\.\\d+)?".r
5.   val FileName="NumberFile"
6.   val path = "src\\"+FileName+".txt"
7.   val FileStr=io.Source.fromFile(path).mkString
8.   val StrArray=pattern2.findAllIn(FileStr).toArray
9.   var total=0d
10.   val len=StrArray.length
11.   StrArray.foreach (total +=_.toDouble)
12.   println("文本中浮点数总和: "+total)
13.   println("文本中浮点数平均数: "+total/len+len)
14.   println("文本中浮点数的最大值: "+StrArray.max)
15.   println("文本中浮点数的最大值: "+StrArray.min)
16. }

测试数据：

joint    55    666.0    management    13.5    committee    12.5

joint    6.0    123.4    management    3.14    committee    170.5

joint    52    63.32    management    10.4    committee    12.5

运行结果：

文本中浮点数总和: 1188.26

文本中浮点数平均数: 99.0216666666666612

文本中浮点数的最大值: 666.0

文本中浮点数的最大值: 10.4

5. 编写Scala程序，向文件中写入2的n次方及其倒数，指数n从0到20。对齐各列:

1 1

2 0.5

4 0.25

... ...

程序代码：

1. import java.io.PrintWriter
2.  
3. object index extends App{
4.   val FileName="Index"
5.   val path="src\\"+FileName+".txt"
6.   val out=new PrintWriter(path)
7.   for (i <- 0 to 20)
8.     out.println(OutIndex(i))
9.   out.close
10.   def OutIndex(n:Int)={
11.     val value=math.pow(2, n)
12.     ""*4+value.toInt+""*(11-value.toString().size)+math.pow(2, -n)
13.   }
14. }

运行结果：

1 1.0

2 0.5

4 0.25

8 0.125

16 0.0625

32 0.03125

64 0.015625

128 0.0078125

256 0.00390625

512 0.001953125

1024 9.765625E-4

2048 4.8828125E-4

4096 2.44140625E-4

8192 1.220703125E-4

16384 6.103515625E-5

32768 3.0517578125E-5

65536 1.52587890625E-5

131072 7.62939453125E-6

262144 3.814697265625E-6

524288 1.9073486328125E-6

1048576 9.5367431640625E-7

6. 编写正则表达式，匹配Java或C++程序代码中类似"like this，maybe with \" or\\"这样的带引号的字符串。编写Scala程序将某个源文件中所有类似的字符串打印出来

描述：没看太懂，按自己意思来的

程序代码：

1. import scala.io.Source
2.  
3. object regExp extends App{
4.   val FileName="Regexp"
5.   val path="src\\"+FileName+".txt"
6.   val pat1=""""like this，maybe with \\" or\\{2}"""".r
7.   val pat2="""like this，maybe with \\" or\\{2}""".r
8.   val pat3="""\w+\s+\\"""".r
9.   val linesIterator1=Source.fromFile(path).getLines()
10.   val linesIterator2=Source.fromFile(path).getLines()
11.   val linesIterator3=Source.fromFile(path).getLines()
12.   println("文本中包含:"+""""like this，maybe with \" or\\"""")
13.   linesIterator1.foreach(line=>pat1.findAllIn(line).foreach (println))
14.   println("文本中包含:"+"""like this，maybe with \" or\\""")
15.   linesIterator2.foreach(line=>pat2.findAllIn(line).foreach (println))
16.   println("文本中包含:"+"\\w+\\s+\"")
17.   linesIterator3.foreach(line=>pat3.findAllIn(line).foreach(println))
18. }

运行结果：

文本中包含:"like this，maybe with \" or\\"

"like this，maybe with \" or\\"

文本中包含:like this，maybe with \" or\\

like this，maybe with \" or\\

like this，maybe with \" or\\

like this，maybe with \" or\\

文本中包含:\w+\s+"

with \"

with \"

with \"

7. 编写Scala程序，从文本文件读取内容，并打印出所有的非浮点数的词法单位。要求使用正则表达式

程序代码：

1. import io.Source
2. object NonFloat extends App{
3.   val source = Source.fromFile("src\\NumberFile.txt").mkString
4.   val pat1 = """[^((\d+\.){0,1}\d+)^\s+]+$""".r//去掉+试试
5.   val pat2 = """^((?!^[-]?\d*\.\d+$).)+$""".r
6.   println("模式1不包含整数:")
7.   for(token <- source.split("\\s+")){
8.     for(word <- pat1.findAllIn(token))
9.       if(!word.equals("")){
10.         println(token)
11.       }
12.   }
13.   println("模式2包含整数:")
14.   for(token <- source.split("\\s+")){
15.     for(word <- pat2.findAllIn(token))
16.       println(word)
17.   }
18. }

测试数据：

joint    55    666.0    management    13.5    committee    12.5

joint    6.0    123.4    management    3.14    committee    170.5

joint    52    63.32    management    10.4    committee    12.5

0.12t    20    5.6ef    45.77ghjss    5.94    dfdxsccxz    7.9

运行结果：

模式1不包含整数:

joint

management

committee

joint

management

committee

joint

management

committee

0.12t

5.6ef

45.77ghjss

dfdxsccxz

模式2包含整数:

joint

55

management

committee

joint

management

committee

joint

52

management

committee

0.12t

20

5.6ef

45.77ghjss

dfdxsccxz

8. 编写Scala程序打印出某个网页中所有img标签的src属性。使用正则表达式和分组

程序代码：

1. object WebSrc extends App{
2.   val pat = """<img.*?src=["‘](.+?)["‘].*?>""".r
3.   for (pat(src) <-pat.findAllIn(io.Source.fromURL("http://www.baidu.com").mkString)) {
4.     println(src)
5.   }
6. }

运行结果：

//www.baidu.com/img/bd_logo1.png

//www.baidu.com/img/baidu_jgylogo3.gif

9. 编写Scala程序，盘点给定目录及其子目录中总共有多少以.class为扩展名的文件

程序代码：

1. import java.io.File
2. object NumDir extends App{
3.   val path = "."
4.   val dir = new File(path)
5.   def subdirs(dir:File):Iterator[File]={
6.     val children = dir.listFiles().filter(_.getName.endsWith("class"))
7.     children.toIterator ++ dir.listFiles().filter(_.isDirectory).toIterator.flatMap(subdirs _)
8.   }
9.   val n = subdirs(dir).length
10.   println(n)
11. }

运行结果：

52

10. 扩展那个可序列化的Person类，让它能以一个集合保存某个人的朋友信息。构造出一些Person对象，让他们中的一些人成为朋友，然后将Array[Person]保存到文件。将这个数组从文件中重新读出来，校验朋友关系是否完好 注意,请在main中执行。脚本执行无法序列化。

程序代码：

1. import collection.mutable.ArrayBuffer
2. import java.io.{ObjectInputStream, FileOutputStream, FileInputStream, ObjectOutputStream}
3.  
4. class Person(var name:String) extends Serializable{
5.   val friends = new ArrayBuffer[Person]()
6.   def addFriend(friend : Person){
7.     friends += friend
8.   }
9.   override def toString() = {
10.     var str = "My name is " + name + " and my friends name is "
11.     friends.foreach(str += _.name + ",")
12.     str
13.   }
14. }
15.  
16. object PersonTest extends App{
17.   val p1 = new Person("JackChen")
18.   val p2 = new Person("Jhon·D")
19.   val p3 = new Person("Sunday")
20.   p1.addFriend(p2)
21.   p1.addFriend(p3)
22.   println(p1)
23.   val out = new ObjectOutputStream(new FileOutputStream("src\\Person.txt"))
24.   out.writeObject(p1)
25.   out.close()
26.   val in = new ObjectInputStream(new FileInputStream("src\\Person.txt"))
27.   val p = in.readObject().asInstanceOf[Person]
28.   println(p)
29. }

运行结果：

My name is JackChen and my friends name is Jhon·D,Sunday,

My name is JackChen and my friends name is Jhon·D,Sunday,

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