|NO.Z.00019|——————————|BigDataEnd|——|Hadoop&Scala.V06|——|Scala.v06|Scala函数|文件操作|

一、文件操作

### --- 导入scala.io.Source后，可引用Source中的方法读取文本文件的内容
~~~     如果要将文件内容转数组，直接调用toArray。

import scala.io.{BufferedSource, Source}
object FileDemo {
    def main(args: Array[String]): Unit = {
        //注意文件的编码格式，如果编码格式不对，那么读取报错
        val file: BufferedSource = Source.fromFile("... ...", "GBK");
    val lines: Iterator[String] = file.getLines()
    for (line <- lines) {
        println(line)
    }
    //注意关闭文件
    file.close()
}
}

### --- 读取网络资源

import scala.io.{BufferedSource, Source}
object FileDemo2 {
    def main(args: Array[String]): Unit = {
        val source: BufferedSource = Source.fromURL("http://www.baidu.com")
        val string: String = source.mkString
    println(string)
    source.close()
}
}

### --- Scala没有内建的对写入文件的支持。要写入文本文件，可使用 java.io.PrintWriter

import java.io.PrintWriter
object FileDemo3 {
    def main(args: Array[String]): Unit = {
        val writer = new PrintWriter("../a.txt")
        for(i <- 1 to 100){
            writer.println(i)
            writer.flush()
        }
    writer.close()
}
}

### --- 编程代码

package yanqi.cn.part02

import java.io.PrintWriter

import scala.io.{BufferedSource, Source}

/**
 * I/O操作是一门编程语言的重要内容
 * 相比于Java语言中的I/O类，Scala中的I/O的类数量较少，最常用的是Source这个类。
 * 在Scala中，更多的是调用Java中的 I/O类或者通过对Java中的I/O类进行相应的封装来实现I/O操作。
 */
object FileDemo {
  //读取文本文件
  def readTextFile: Unit = {
    val file = Source.fromFile("src\\text.txt")
    val lines: Iterator[String] = file.getLines()

    for (line <- lines) {
      println(line)
    }
    //关闭文件
    file.close()
  }

  //读取网络资源，需要在联网状态下
  def readNetSource: Unit = {
    val source: BufferedSource = Source.fromURL("http://www.baidu.com")
    val message: String = source.mkString

    println(message)

    source.close()
  }

  //写入文本文件
  //Scala中没有内建的对写入文件的支持，需要使用java.io.PrintWriter来实现
  def writeTextFile: Unit = {
    val writer = new PrintWriter("src\\text.txt")
    for (i <- 1 to 10) {
      //写入文件内容
      writer.println(s"i = $i")
      //刷新printwriter流的缓冲区
      writer.flush()
    }

    //关闭写入流
    writer.close()
  }

  def main(args: Array[String]): Unit = {
    readTextFile
    println("==================================")
    readNetSource
    println("==================================")
    writeTextFile
  }
}

### --- 编译打印

D:\JAVA\jdk1.8.0_231\bin\java.exe "-javaagent:D:\IntelliJIDEA\IntelliJ IDEA 2019.3.3\lib\idea_rt.jar=53431:D:\IntelliJIDEA\IntelliJ IDEA 2019.3.3\bin" -Dfile.encoding=UTF-8 -classpath D:\JAVA\jdk1.8.0_231\jre\lib\charsets.jar;D:\JAVA\jdk1.8.0_231\jre\lib\deploy.jar;D:\JAVA\jdk1.8.0_231\jre\lib\ext\access-bridge-64.jar;D:\JAVA\jdk1.8.0_231\jre\lib\ext\cldrdata.jar;D:\JAVA\jdk1.8.0_231\jre\lib\ext\dnsns.jar;D:\JAVA\jdk1.8.0_231\jre\lib\ext\jaccess.jar;D:\JAVA\jdk1.8.0_231\jre\lib\ext\jfxrt.jar;D:\JAVA\jdk1.8.0_231\jre\lib\ext\localedata.jar;D:\JAVA\jdk1.8.0_231\jre\lib\ext\nashorn.jar;D:\JAVA\jdk1.8.0_231\jre\lib\ext\sunec.jar;D:\JAVA\jdk1.8.0_231\jre\lib\ext\sunjce_provider.jar;D:\JAVA\jdk1.8.0_231\jre\lib\ext\sunmscapi.jar;D:\JAVA\jdk1.8.0_231\jre\lib\ext\sunpkcs11.jar;D:\JAVA\jdk1.8.0_231\jre\lib\ext\zipfs.jar;D:\JAVA\jdk1.8.0_231\jre\lib\javaws.jar;D:\JAVA\jdk1.8.0_231\jre\lib\jce.jar;D:\JAVA\jdk1.8.0_231\jre\lib\jfr.jar;D:\JAVA\jdk1.8.0_231\jre\lib\jfxswt.jar;D:\JAVA\jdk1.8.0_231\jre\lib\jsse.jar;D:\JAVA\jdk1.8.0_231\jre\lib\management-agent.jar;D:\JAVA\jdk1.8.0_231\jre\lib\plugin.jar;D:\JAVA\jdk1.8.0_231\jre\lib\resources.jar;D:\JAVA\jdk1.8.0_231\jre\lib\rt.jar;E:\NO.Z.10000——javaproject\NO.Z.00002.Hadoop\ScalaPro\out\production\ScalaPro;D:\JAVA\scala-2.12.2\lib\scala-library.jar;D:\JAVA\scala-2.12.2\lib\scala-reflect.jar yanqi.cn.part02.FileDemo
i = 1
i = 2
i = 3
i = 4
i = 5
i = 6
i = 7
i = 8
i = 9
i = 10
==================================
<!DOCTYPE html>
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==================================

Process finished with exit code 0

Walter Savage Landor:strove with none,for none was worth my strife.Nature I loved and, next to Nature, Art:I warm'd both hands before the fire of life.It sinks, and I am ready to depart

——W.S.Landor