{"id":14270,"date":"2018-04-21T06:07:20","date_gmt":"2018-04-21T06:07:20","guid":{"rendered":"https:\/\/data-flair.training\/blogs\/?p=14270"},"modified":"2021-12-04T10:16:23","modified_gmt":"2021-12-04T04:46:23","slug":"scala-file-io","status":"publish","type":"post","link":"https:\/\/data-flair.training\/blogs\/scala-file-io\/","title":{"rendered":"Scala File i\/o: Open, Read and Write a File in Scala"},"content":{"rendered":"

In this tutorial Scala File io, we will learn how to Open, read and write files in Scala. I also recommend you to go through the Scala Syntax <\/a><\/strong>and Scala Functions <\/a><\/strong>Articles to clear your basics on Scala.<\/p>\n

So, let’s start Scala File io Tutorial.<\/p>\n

Opening and Writing to a File in Scala<\/h3>\n

We don\u2019t have a class to write a file, in the Scala standard library, so we borrow java.io._ from Java. Or you could import java.io.File and java.io.PrintWriter.<\/p>\n

a. The Import<\/h4>\n
C:\\Users\\lifei>cd Desktop\r\nC:\\Users\\lifei\\Desktop>scala<\/pre>\n
Welcome to Scala 2.12.5 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_161).<\/p>\n
Type in expressions for evaluation. Or try :help.<\/p>\n
scala> import java.io._\r\nimport java.io._<\/pre>\n
Learn: Scala Data Types with Examples<\/a><\/strong><\/h3>\n
b. Creating a New File in Scala<\/h4>\n
To create a new file to write to, we create a new instance of PrintWriter, and pass a new File object to it.<\/p>\n
scala> val writer=new PrintWriter(new File(\"demo1.txt\"))\r\nwriter: java.io.PrintWriter = java.io.PrintWriter@31c7c281<\/pre>\n
c. Writing to the File in Scala<\/h4>\n
Now, to write to the file, we call the method write() on the object we created.<\/p>\n
scala> writer.write(\"This is a demo\")<\/pre>\n
d. Finally<\/h4>\n
At this point, nothing is really visible in the file. To see these changes reflect in the file demo1.txt, we need to close it with Scala.<\/p>\n
scala> writer.close()<\/pre>\n
Now, when we check the file demo1.txt again, we find:<\/p>\n
This is a demo<\/p>\n
Together, the code looks something like this:<\/p>\n
C:\\Users\\lifei>cd Desktop\r\nC:\\Users\\lifei\\Desktop>scala<\/pre>\n
Welcome to Scala 2.12.5 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_161).<\/p>\n
Type in expressions for evaluation. Or try :help.<\/p>\n
scala> import java.io._\r\nimport java.io._\r\nscala> val writer=new PrintWriter(new File(\"demo1.txt\"))\r\nwriter: java.io.PrintWriter = java.io.PrintWriter@31c7c281\r\nscala> writer.write(\"This is a demo\")\r\nscala> writer.close()<\/pre>\n
Learn: Scala Variables with Examples<\/a><\/strong><\/p>\n
Reading From a File in Scala<\/h3>\n
Now Scala does provide a class to read files. This is the class Source. We use its companion object to read files. For this demonstration, we\u2019re going to read what we put in the file demo1.txt. Let\u2019s begin.<\/p>\n
a. The Import<\/h4>\n
The class we need to import here is scala.io.Source.<\/p>\n
scala> import scala.io.Source\r\nimport scala.io.Source<\/pre>\n
b. Reading From the File<\/h4>\n
To read the contents of this file, we call the fromFile() method of class Source- with the filename as argument. On this, we call the method mkString, like we\u2019ve seen in different collections so far.<\/p>\n
scala> Source.fromFile(\"demo1.txt\").mkString\r\nres4: String = This is a demo<\/pre>\n
c. Reading Between The Lines (Pun Intended)<\/h4>\n
To read individual lines instead of the whole file at once, we can use the getLines() method. For this, \u00a0we change the contents of our file to this:<\/p>\n
This is a demo<\/p>\n
This is line 2<\/p>\n
And this is line 3<\/p>\n
The code we use is:<\/p>\n
scala> Source.fromFile(\"demo1.txt\").getLines.foreach{x=>println(x)}<\/pre>\n
This is a demo<\/p>\n
This is line 2<\/p>\n
And this is line 3<\/p>\n
Learn: Scala String Interpolation<\/a><\/strong><\/h3>\n
d. Using an Iterator<\/h4>\n
We can also make use of an iterator to get one line at a time:<\/p>\n
scala> val it=Source.fromFile(\"demo1.txt\").getLines()\r\nit: Iterator[String] = non-empty iterator\r\nscala> it.next()\r\nres9: String = This is a demo\r\nscala> it.next()\r\nres10: String = This is line 2\r\nscala> it.next()\r\nres11: String = And this is line 3\r\nscala> it.next()<\/pre>\n
java.util.NoSuchElementException: next on empty iterator\r\n at scala.collection.Iterator$$anon$2.next(Iterator.scala:38)\r\n at scala.collection.Iterator$$anon$2.next(Iterator.scala:36)\r\n at scala.io.BufferedSource$BufferedLineIterator.next(BufferedSource.scala:79)\r\n at scala.io.BufferedSource$BufferedLineIterator.next(BufferedSource.scala:64)\r\n ... 28 elided<\/pre>\n
e. Extracting Individual Lines with take()<\/h4>\n
When we talked iterators, we saw the use of the method take(n) to return the first n values from the iterator. This is what we\u2019re going to use here.<\/p>\n
scala> val it=Source.fromFile(\"demo1.txt\").getLines.take(2)\r\nit: Iterator[String] = non-empty iterator\r\nscala> while(it.hasNext){print(it.next())}<\/pre>\n
This is a demoThis is line 2<\/p>\n
If we passed 1 to take(), it would only print \u201cThis is a demo\u201d.<\/p>\n
f. Extracting Individual Lines with slice(start,until)<\/h4>\n
The method slice(start,until) returns an iterator over lines start<\/i> to until<\/i>-1.<\/p>\n
scala> val it=Source.fromFile(\"demo1.txt\").getLines.slice(1,3)\r\nit: Iterator[String] = non-empty iterator\r\nscala> while(it.hasNext){print(it.next())}<\/pre>\n
This is line 2And this is line 3<\/p>\n
So, this was all on Scala File io Tutorial. Hope you like our explanation.<\/p>\n
Conclusion<\/h3>\n
So this is how you read and write a Scala file io. In this article, we saw use of methods write(), close(), fromFile(), getLines(), take(), and slice(). Furthermore, if you have any query, feel free to ask in the comment section.<\/p>\n
For Reference<\/a><\/strong>
In this tutorial Scala File io, we will learn how to Open, read and write files in Scala. I also recommend you to go through the Scala Syntax and Scala Functions Articles to clear...<\/p>\n","protected":false},"author":6,"featured_media":34739,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[61],"tags":[3115,9272,11377,12449],"class_list":["post-14270","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-scala","tag-creating-a-new-file","tag-opening-and-writing-to-a-file","tag-reading-from-the-file","tag-scala-file-io"],"yoast_head":"\nScala File i\/o: Open, Read and Write a File in Scala - DataFlair<\/title>\n<meta name=\"description\" content=\"Scala File io:Learn to Open, read and write files in Scala. 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