scala 写入文件_Scala文件IO –写入文件，读取文件

scala 写入文件

Today we will look into Scala File IO operations. File operations mainly include reading data from files or writing data into files. Here we will look into Scala read file and Scala write file programs.

今天，我们将研究Scala File IO操作。文件操作主要包括从文件读取数据或将数据写入文件。在这里，我们将研究Scala读取文件和Scala写入文件程序。

Scala文件IO (Scala File IO)

Scala读取文件 (Scala Read File)

We can use scala.io.Source to read data from a file. For reading a file, we have created a test file with below content.

我们可以使用scala.io.Source从文件中读取数据。为了读取文件，我们创建了一个包含以下内容的测试文件。

data.txt

JournalDev is a great platform for Java Developers.
JournalDev is online log of Pankaj Kumar.

Here is a simple program where we are using Scala Source class to read file data to a String and then split it using regular expression to a Map. Finally we are printing the count of JournalDev in the file content.

这是一个简单的程序，其中我们使用Scala Source类将文件数据读取为String，然后使用正则表达式将其拆分为Map。最后，我们在文件内容中打印JournalDev的计数。

Wordcount.scala

import scala.io.Sourceobject Wordcount {def main(args:Array[String]) {println(Source.fromFile("data.txt")) // returns scala.io.BufferedSource non-empty iterator instanceval s1 = Source.fromFile("data.txt").mkString; //returns the file data as Stringprintln(s1)//splitting String data with white space and calculating the number of occurrence of each word in the file  val counts = s1.split("\\s+").groupBy(x=>x).mapValues(x=>x.length) println(counts)println("Count of JournalDev word:"+counts("JournalDev"))}}

Below image shows the execution of Scala read file program and output.

下图显示了Scala读取文件程序的执行和输出。

Word count line by line: Sometimes there arises a need to process each line rather than the whole contents of the file. This can be achieved through the getLines method. For example below code;

逐行单词计数 ：有时需要处理每一行而不是文件的全部内容。这可以通过getLines方法实现。例如下面的代码；

println(Source.fromFile("data.txt").getLines())Source.fromFile("data.txt").getLines.foreach { x => println(x) };

will produce following output;

将产生以下输出；

non-empty iterator
JournalDev is a great platform for Java Developers.
JournalDev is online log of Pankaj Kumar.

Now let us see how to extract specific set of lines.

现在让我们看看如何提取特定的线集。

Source.fromFile("data.txt").getLines.take(1).foreach { x => println(x) };
Source.fromFile("data.txt").getLines.slice(0, 1).foreach { x => println(x) };

take(n) method is used to Select first n values of the iterator where slice(from, until) returns part of the iterator where “from” index is the part of slice and “until” index is not. So both the lines in above code snippet are doing the same thing.

take(n)方法用于选择迭代器的前n个值，其中slice(from, until)返回迭代器的一部分，其中“ from”索引是slice的一部分，而“ until”索引不是。因此，以上代码片段中的两行都在做相同的事情。

Scala写入文件 (Scala Write to File)

Scala standard library doesn’t contain any classes to write files, so we will use Java IO classes for scala write to file. Below is a simple program showing how to write files in scala.

Scala标准库不包含任何用于写入文件的类，因此我们将使用Java IO类将Scala写入文件。下面是一个简单的程序，显示了如何在Scala中写入文件。

Write.scala

import java.io.File
import java.io.PrintWriterimport scala.io.Sourceobject Write {def main(args: Array[String]) {val writer = new PrintWriter(new File("Write.txt"))writer.write("Hello Developer, Welcome to Scala Programming.")writer.close()Source.fromFile("Write.txt").foreach { x => print(x) }}}

This will produce a file Write.txt with given content and then Source will read and print the same file data.

这将产生具有给定内容的文件Write.txt，然后Source将读取并打印相同的文件数据。

That’s all for Scala File IO example. You can see how simple it is to read file in Scala and write file in Scala using Java IO classes.

这就是Scala File IO示例的全部内容。您可以看到使用Java IO类在Scala中读取文件和在Scala中写入文件有多么简单。

翻译自: https://www.journaldev.com/8278/scala-file-io-write-file-read-file

scala 写入文件