blocks|key|832672|text|这是标准Scala中缺少的特性之一，我发现它非常有用，所以我将其添加到了我的个人库中。(您可能也应该有一个个人库。)代码是这样的：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|832673|def+printToFile(f:+java.io.File)(op:+java.io.PrintWriter+=>+Unit)+{
++val+p+=+new+java.io.PrintWriter(f)
++try+{+op(p)+}+finally+{+p.close()+}
}|code-block|syntax|javascript|832674|它的用法如下：|832675|import+java.io._
val+data+=+Array("Five","strings","in","a","file!")
printToFile(new+File("example.txt"))+{+p+=>
++data.foreach(p.println)
}|832676|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

This is one of the features missing from standard Scala that I have found so useful that I add it to my personal library. (You probably should have a personal library, too.) The code goes like so:

<pre><code>def printToFile(f: java.io.File)(op: java.io.PrintWriter =&gt; Unit) {
 val p = new java.io.PrintWriter(f)
 try { op(p) } finally { p.close() }
}
</code></pre>

and it's used like this:

<pre><code>import java.io._
val data = Array("Five","strings","in","a","file!")
printToFile(new File("example.txt")) { p =&gt;
 data.foreach(p.println)
}
</code></pre>

blocks|key|1047577|text|与Rex+Kerr的答案类似，但更通用。首先，我使用一个helper函数：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1047578|/**
+*+Used+for+reading/writing+to+database,+files,+etc.
+*+Code+From+the+book+"Beginning+Scala"
+*+http://www.amazon.com/Beginning-Scala-David-Pollak/dp/1430219890
+*/
def+using[A+<:+{def+close():+Unit},+B](param:+A)(f:+A+=>+B):+B+=
try+{+f(param)+}+finally+{+param.close()+}|code-block|syntax|javascript|1047579|然后，我将其用作：|1047580|def+writeToFile(fileName:String,+data:String)+=+
++using+(new+FileWriter(fileName))+{
++++fileWriter+=>+fileWriter.write(data)
++}|1047581|和|1047582|def+appendToFile(fileName:String,+textData:String)+=
++using+(new+FileWriter(fileName,+true)){+
++++fileWriter+=>+using+(new+PrintWriter(fileWriter))+{
++++++printWriter+=>+printWriter.println(textData)
++++}
++}|1047583|等。|1047584|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|W|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|Y|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

Similar to the answer by Rex Kerr, but more generic. First I use a helper function:

<pre><code>/**
 * Used for reading/writing to database, files, etc.
 * Code From the book "Beginning Scala"
 * http://www.amazon.com/Beginning-Scala-David-Pollak/dp/1430219890
 */
def using[A &lt;: {def close(): Unit}, B](param: A)(f: A =&gt; B): B =
try { f(param) } finally { param.close() }
</code></pre>

Then I use this as:

<pre><code>def writeToFile(fileName:String, data:String) = 
 using (new FileWriter(fileName)) {
 fileWriter =&gt; fileWriter.write(data)
 }
</code></pre>

and 

<pre><code>def appendToFile(fileName:String, textData:String) =
 using (new FileWriter(fileName, true)){ 
 fileWriter =&gt; using (new PrintWriter(fileWriter)) {
 printWriter =&gt; printWriter.println(textData)
 }
 }
</code></pre>

etc.

blocks|key|832733|text|一个简单的答案：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|832734|import+java.io.File
import+java.io.PrintWriter

def+writeToFile(p:+String,+s:+String):+Unit+=+{
++++val+pw+=+new+PrintWriter(new+File(p))
++++try+pw.write(s)+finally+pw.close()
++}|code-block|syntax|javascript|832735|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

A simple answer:

<pre><code>import java.io.File
import java.io.PrintWriter

def writeToFile(p: String, s: String): Unit = {
 val pw = new PrintWriter(new File(p))
 try pw.write(s) finally pw.close()
 }
</code></pre>

blocks|key|1047631|text|下面是一个使用Scala编译器库的简洁的一行代码：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1047632|scala.tools.nsc.io.File("filename").writeAll("hello+world")|code-block|syntax|javascript|1047633|或者，如果你想使用Java库，你可以这样做：|1047634|Some(new+PrintWriter("filename")).foreach{p+=>+p.write("hello+world");+p.close}|1047635|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Here is a concise one-liner using the Scala compiler library:

<pre><code>scala.tools.nsc.io.File("filename").writeAll("hello world")
</code></pre>

Alternatively, if you want to use the Java libraries you can do this hack:

<pre><code>Some(new PrintWriter("filename")).foreach{p =&gt; p.write("hello world"); p.close}
</code></pre>

blocks|key|832844|text|一行代码，用于存储/读取String，使用java.nio。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|832845|import+java.nio.file.{Paths,+Files,+StandardOpenOption}
import+java.nio.charset.{StandardCharsets}
import+scala.collection.JavaConverters._

def+write(filePath:String,+contents:String)+=+{
++Files.write(Paths.get(filePath),+contents.getBytes(StandardCharsets.UTF_8),+StandardOpenOption.CREATE)
}

def+read(filePath:String):String+=+{
++Files.readAllLines(Paths.get(filePath),+StandardCharsets.UTF_8).asScala.mkString
}|code-block|syntax|javascript|832846|这不适合大文件，但可以做这项工作。|832847|一些链接：|832848|java.nio.file.Files.write|832849|java.lang.String.getBytes|832850|scala.collection.JavaConverters|832851|scala.collection.immutable.List.mkString|832852|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.oracle.com/javase/7/docs/api/java/nio/file/Files.html#write%2528java.nio.file.Path,%2520byte%255B%255D,%2520java.nio.file.OpenOption...%2529|1|http://docs.oracle.com/javase/7/docs/api/java/lang/String.html#getBytes%2528java.nio.charset.Charset%2529|2|http://www.scala-lang.org/api/current/index.html#scala.collection.JavaConverters$|3|http://www.scala-lang.org/api/current/index.html#scala.collection.immutable.List^0|C|6|L|8|0|0|0|0|0|P|0|0|0|P|1|0|0|V|2|0|0|14|3|0^^$0|@$1|2|3|4|5|6|7|1A|8|@$9|1B|A|1C|B|C]|$9|1D|A|1E|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|1F|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|1G|8|@]|D|@]|E|$]]|$1|M|3|N|5|6|7|1H|8|@]|D|@]|E|$]]|$1|O|3|P|5|6|7|1I|8|@]|D|@$9|1J|A|1K|1|1L]]|E|$]]|$1|Q|3|R|5|6|7|1M|8|@]|D|@$9|1N|A|1O|1|1P]]|E|$]]|$1|S|3|T|5|6|7|1Q|8|@]|D|@$9|1R|A|1S|1|1T]]|E|$]]|$1|U|3|V|5|6|7|1U|8|@]|D|@$9|1V|A|1W|1|1X]]|E|$]]|$1|W|3|-4|5|6|7|1Y|8|@]|D|@]|E|$]]]|X|$Y|$5|Z|10|11|E|$12|13]]|14|$5|Z|10|11|E|$12|15]]|16|$5|Z|10|11|E|$12|17]]|18|$5|Z|10|11|E|$12|19]]]]

One liners for saving/reading to/from <code>String</code>, using <code>java.nio</code>.

<pre><code>import java.nio.file.{Paths, Files, StandardOpenOption}
import java.nio.charset.{StandardCharsets}
import scala.collection.JavaConverters._

def write(filePath:String, contents:String) = {
 Files.write(Paths.get(filePath), contents.getBytes(StandardCharsets.UTF_8), StandardOpenOption.CREATE)
}

def read(filePath:String):String = {
 Files.readAllLines(Paths.get(filePath), StandardCharsets.UTF_8).asScala.mkString
}
</code></pre>

This isn't suitable for large files, but will do the job.

Some links:

<a href="http://docs.oracle.com/javase/7/docs/api/java/nio/file/Files.html#write%28java.nio.file.Path,%20byte%5B%5D,%20java.nio.file.OpenOption...%29" rel="noreferrer">java.nio.file.Files.write</a> 
<a href="http://docs.oracle.com/javase/7/docs/api/java/lang/String.html#getBytes%28java.nio.charset.Charset%29" rel="noreferrer">java.lang.String.getBytes</a> 
<a href="http://www.scala-lang.org/api/current/index.html#scala.collection.JavaConverters$" rel="noreferrer">scala.collection.JavaConverters</a> 
<a href="http://www.scala-lang.org/api/current/index.html#scala.collection.immutable.List" rel="noreferrer">scala.collection.immutable.List.mkString</a>

blocks|key|832891|text|为了超越samthebest和他之前的贡献者，我改进了命名和简洁性：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|832892|++def+using[A+<:+{def+close()+:+Unit},+B](resource:+A)(f:+A+=>+B):+B+=
++++try+f(resource)+finally+resource.close()

++def+writeStringToFile(file:+File,+data:+String,+appending:+Boolean+=+false)+=
++++using(new+FileWriter(file,+appending))(_.write(data))|code-block|syntax|javascript|832893|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

To surpass samthebest and the contributors before him, I have improved the naming and conciseness:

<pre><code> def using[A &lt;: {def close() : Unit}, B](resource: A)(f: A =&gt; B): B =
 try f(resource) finally resource.close()

 def writeStringToFile(file: File, data: String, appending: Boolean = false) =
 using(new FileWriter(file, appending))(_.write(data))
</code></pre>

blocks|key|832938|text|下面是一个使用scalaz-stream将一些行写入文件的示例。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|832939|import+scalaz._
import+scalaz.stream._

def+writeLinesToFile(lines:+Seq[String],+file:+String):+Task[Unit]+=
++Process(lines:+_*)++++++++++++++//+Process+that+enumerates+the+lines
++++.flatMap(Process(_,+"\n"))++++//+Add+a+newline+after+each+line
++++.pipe(text.utf8Encode)++++++++//+Encode+as+UTF-8
++++.to(io.fileChunkW(fileName))++//+Buffered+write+to+the+file
++++.runLog[Task,+Unit]+++++++++++//+Get+this+computation+as+a+Task
++++.map(_+=>+())+++++++++++++++++//+Discard+the+result

writeLinesToFile(Seq("one",+"two"),+"file.txt").run|code-block|syntax|javascript|832940|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/scalaz/scalaz-stream^0|7|D|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

Here's an example of writing some lines to a file using <a href="https://github.com/scalaz/scalaz-stream" rel="nofollow">scalaz-stream</a>.

<pre><code>import scalaz._
import scalaz.stream._

def writeLinesToFile(lines: Seq[String], file: String): Task[Unit] =
 Process(lines: _*) // Process that enumerates the lines
 .flatMap(Process(_, "\n")) // Add a newline after each line
 .pipe(text.utf8Encode) // Encode as UTF-8
 .to(io.fileChunkW(fileName)) // Buffered write to the file
 .runLog[Task, Unit] // Get this computation as a Task
 .map(_ =&gt; ()) // Discard the result

writeLinesToFile(Seq("one", "two"), "file.txt").run
</code></pre>

blocks|key|1047801|text|我写的一个微库：https://github.com/pathikrit/better-files|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1047802|file.appendLine("Hello",+"World")|code-block|syntax|javascript|1047803|或|1047804|file+<<+"Hello"+<<+"\n"+<<+"World"|1047805|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/pathikrit/better-files^0|8|15|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@$A|V|B|W|1|X]]|C|$]]|$1|D|3|E|5|F|7|Y|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|Z|8|@]|9|@]|C|$]]|$1|K|3|L|5|F|7|10|8|@]|9|@]|C|$G|H]]|$1|M|3|-4|5|6|7|11|8|@]|9|@]|C|$]]]|N|$O|$5|P|Q|R|C|$S|T]]]]

A micro library I wrote: <a href="https://github.com/pathikrit/better-files" rel="noreferrer">https://github.com/pathikrit/better-files</a>

<pre><code>file.appendLine("Hello", "World")
</code></pre>

or

<pre><code>file &lt;&lt; "Hello" &lt;&lt; "\n" &lt;&lt; "World"
</code></pre>

blocks|key|832992|text|这一行有助于从数组或字符串中写入文件。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|832993|+new+PrintWriter(outputPath)+{+write(ArrayName.mkString(""));+close+}|code-block|syntax|javascript|832994|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

This line helps to write a file from an Array or String.

<pre><code> new PrintWriter(outputPath) { write(ArrayName.mkString("")); close }
</code></pre>

blocks|key|1047870|text|如果你的项目中有Akka+Streams，它提供了一行：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1047871|def+writeToFile(p:+Path,+s:+String)(implicit+mat:+Materializer):+Unit+=+{
++Source.single(ByteString(s)).runWith(FileIO.toPath(p))
}|code-block|syntax|javascript|1047872|Akka文档>+Streaming+File+IO|offset|length|1047873|entityMap|0|LINK|mutability|MUTABLE|url|https://doc.akka.io/docs/akka/current/stream/stream-io.html?language=scala#streaming-file-io^0|0|0|8|H|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@$I|V|J|W|1|X]]|A|$]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]]]

If you are anyways having Akka Streams in your project, it provides a one-liner:

<pre><code>def writeToFile(p: Path, s: String)(implicit mat: Materializer): Unit = {
 Source.single(ByteString(s)).runWith(FileIO.toPath(p))
}
</code></pre>

Akka docs > <a href="https://doc.akka.io/docs/akka/current/stream/stream-io.html?language=scala#streaming-file-io" rel="nofollow noreferrer">Streaming File IO</a>

blocks|key|1047924|text|不幸的是，最重要的答案是Scala-IO已经死了。如果您不介意使用第三方依赖项，可以考虑使用我的OS-Lib+library。这使得处理文件、路径和文件系统变得非常容易：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1047925|//+Make+sure+working+directory+exists+and+is+empty
val+wd+=+os.pwd/"out"/"splash"
os.remove.all(wd)
os.makeDir.all(wd)

//+Read/write+files
os.write(wd/"file.txt",+"hello")
os.read(wd/"file.txt")+==>+"hello"

//+Perform+filesystem+operations
os.copy(wd/"file.txt",+wd/"copied.txt")
os.list(wd)+==>+Seq(wd/"copied.txt",+wd/"file.txt")|code-block|syntax|javascript|1047926|它为writing+to+files、appending+to+files、overwriting+files和许多其他有用/常见的操作提供了一行程序|1047927|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/lihaoyi/os-lib|1|https://github.com/lihaoyi/os-lib#oswrite|2|https://github.com/lihaoyi/os-lib#oswriteappend|3|https://github.com/lihaoyi/os-lib#oswriteover^0|1C|E|0|0|0|2|G|1|J|I|2|12|H|3|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@$A|Z|B|10|1|11]]|C|$]]|$1|D|3|E|5|F|7|12|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|13|8|@]|9|@$A|14|B|15|1|16]|$A|17|B|18|1|19]|$A|1A|B|1B|1|1C]]|C|$]]|$1|K|3|-4|5|6|7|1D|8|@]|9|@]|C|$]]]|L|$M|$5|N|O|P|C|$Q|R]]|S|$5|N|O|P|C|$Q|T]]|U|$5|N|O|P|C|$Q|V]]|W|$5|N|O|P|C|$Q|X]]]]

Unfortunately for the top answer, Scala-IO is dead. If you don't mind using a third-party dependency, consider using my <a href="https://github.com/lihaoyi/os-lib" rel="noreferrer">OS-Lib library</a>. This makes working with files, paths and the filesystem very easy:

<pre><code>// Make sure working directory exists and is empty
val wd = os.pwd/"out"/"splash"
os.remove.all(wd)
os.makeDir.all(wd)

// Read/write files
os.write(wd/"file.txt", "hello")
os.read(wd/"file.txt") ==&gt; "hello"

// Perform filesystem operations
os.copy(wd/"file.txt", wd/"copied.txt")
os.list(wd) ==&gt; Seq(wd/"copied.txt", wd/"file.txt")
</code></pre>

It has one-liners for <a href="https://github.com/lihaoyi/os-lib#oswrite" rel="noreferrer">writing to files</a>, <a href="https://github.com/lihaoyi/os-lib#oswriteappend" rel="noreferrer">appending to files</a>, <a href="https://github.com/lihaoyi/os-lib#oswriteover" rel="noreferrer">overwriting files</a>, and many other useful/common operations

blocks|key|833144|text|与this+answer类似，下面是一个使用fs2+(版本1.0.4)的示例：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|833145|import+cats.effect._

import+fs2._
import+fs2.io

import+java.nio.file._

import+scala.concurrent.ExecutionContext
import+scala.language.higherKinds
import+cats.syntax.functor._

object+ScalaApp+extends+IOApp+{

++def+write[T[_]](p:+Path,+s:+String)
+++++++++++++++++(implicit+F:+ConcurrentEffect[T],+cs:+ContextShift[T]):+T[Unit]+=+{
++++Stream(s)
++++++.covary[T]
++++++.through(text.utf8Encode)
++++++.through(
++++++++io.file.writeAll(
++++++++++p,
++++++++++scala.concurrent.ExecutionContext.global,
++++++++++Seq(StandardOpenOption.CREATE)
++++++++)
++++++)
++++++.compile
++++++.drain
++}


++def+run(args:+List[String]):+IO[ExitCode]+=+{

++++implicit+val+executionContext:+ExecutionContext+=
++++++scala.concurrent.ExecutionContext.Implicits.global

++++implicit+val+contextShift:+ContextShift[IO]+=
++++++IO.contextShift(executionContext)

++++val+outputFile:+Path+=+Paths.get("output.txt")

++++write[IO](outputFile,+"Hello+world\n").as(ExitCode.Success)

++}
}|code-block|syntax|javascript|833146|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/32265975/5826349^0|M|3|1|B|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]]|D|@$9|V|A|W|1|X]]|E|$]]|$1|F|3|G|5|H|7|Y|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Z|8|@]|D|@]|E|$]]]|L|$M|$5|N|O|P|E|$Q|R]]]]

Similar to <a href="https://stackoverflow.com/a/32265975/5826349">this answer</a>, here is an example with <code>fs2</code> (version 1.0.4):

<pre class="lang-scala prettyprint-override"><code>import cats.effect._

import fs2._
import fs2.io

import java.nio.file._

import scala.concurrent.ExecutionContext
import scala.language.higherKinds
import cats.syntax.functor._

object ScalaApp extends IOApp {

 def write[T[_]](p: Path, s: String)
 (implicit F: ConcurrentEffect[T], cs: ContextShift[T]): T[Unit] = {
 Stream(s)
 .covary[T]
 .through(text.utf8Encode)
 .through(
 io.file.writeAll(
 p,
 scala.concurrent.ExecutionContext.global,
 Seq(StandardOpenOption.CREATE)
 )
 )
 .compile
 .drain
 }


 def run(args: List[String]): IO[ExitCode] = {

 implicit val executionContext: ExecutionContext =
 scala.concurrent.ExecutionContext.Implicits.global

 implicit val contextShift: ContextShift[IO] =
 IO.contextShift(executionContext)

 val outputFile: Path = Paths.get("output.txt")

 write[IO](outputFile, "Hello world\n").as(ExitCode.Success)

 }
}
</code></pre>

For reading, there is the useful abstraction <code>Source</code>. How can I write lines to a text file?

How to write to a file in Scala?

文件系统

编译器

Java

对于阅读，有一个有用的抽象Source。如何将行写入文本文件？

问如何在Scala中写入文件？
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