Scala IO

妖狐艹你老母 2021-09-23 08:28 276阅读 0赞

**目录**

*  1. 读
 *  Source.fromFile
 *  按行读取
 *  读取为字符
 *  读取为字符串
 *  Source读取其他源
 *  Java API
 *  FileInputStream
 *  FileReader
 *  2. 写
 *  FileWrite 
 *  PrintWriter 
 *  RandomAccessFile

--------------------

# 1. 读 #

## **Source.fromFile** ##

可以读取源包括：File，String，URI，并且可以指定编码和读取文件的长度。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpbmdlaW8_size_16_color_FFFFFF_t_70][]

Source.fromFile 读取的数据也可以转换为很多方式。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpbmdlaW8_size_16_color_FFFFFF_t_70 1][]

### 按行读取 ###

import scala.io.Source
    
    object TestRead {
      def main(args: Array[String]): Unit = {
    
        val source = Source.fromFile("d://data/word.txt", "utf-8")
        val lineIterator = source.getLines
        while (lineIterator.hasNext) {
          val line = lineIterator.next()
          println(line)
        }
    
        source.close
      }
    }
    
    // IMEI,356145080566857
    // IDFA,1E2DFA89-496A-47FD-9941-DF1FC4E6484A

### 读取为字符 ###

val source = Source.fromFile("d://data//word.txt")
    
        val byteIterator = source.buffered
        while (byteIterator.hasNext) {
          val byte = byteIterator.next
          println(byte)
        }
    
        source.close

### 读取为字符串 ###

val source = Source.fromFile("d://data//word.txt")
    
        val strArr = source.mkString.split("\n")
        for(str <- strArr) println(str)
    
        // 读取到数组
        val strArray = for(str <- strArr) yield str
        strArray.foreach(println)
    
        source.close

## Source读取其他源 ##

// 读取字符
        val byteArray = Array[Byte]('1','a')
        Source.fromBytes(byteArray)
    
        // 读取流
        val inputStream:InputStream = new FileInputStream("d://data/word.txt")
        Source.fromInputStream(inputStream)
    
        // 读取URL
        val url = new URL("http://baidu.com")
        val sourceUrl = Source.fromURL(url)
        sourceUrl.foreach(print)
    
        // 读取URI
        val uri = new URI(...)
        val sourceUri = Source.fromURI(uri)
    
        //source.close

## Java API ##

> InputStream 以字节流方式读取，读入的是一个字节（二进制），组成 byte 数组（byte：8位）。Reader 将文件以字符流方式读入，读入的是 char数组（char：16位，Unicode编码）或 String。  
> InputStreamReader 是 Reader 和 Stream 之间的转换流，可以将 Stream 转换成字符流方式，可以指定转换编码。

### FileInputStream ###

// val file = new File("d://data//word.txt")
        // val inputStream = new FileInputStream(file)                         // 流,二进制读取
        // val inputStreamReader = new InputStreamReader(inputStream,"utf8")   // 转换流为Reader
        // val bufferedReader = new BufferedReader(inputStreamReader)          // 转换为BufferReader
    
        // 通常 FileInputStream和 InputStreamReader对象只使用一次,所以不定义对象
        val bufferedReader = new BufferedReader(new InputStreamReader(new FileInputStream("d://data//word.txt")))
    
        var result = ""
        result += Stream.continually(bufferedReader.readLine()).takeWhile(_ != null).mkString("\n")
        println(result)
    
        bufferedReader.close()

### FileReader ###

// val file = new File("d://data//word.txt")
        // val fileReader = new FileReader(file)
        // val bufferedReader = new BufferedReader(fileReader)
    
        // 如果 InputStreamReader和FileReader 对象只使用一次,不定义对象
        val bufferedReader = new BufferedReader(new FileReader("d://data//word.txt"))
    
        var result = ""
        result += Stream.continually(bufferedReader.readLine()).takeWhile(_ != null).mkString("\n")
        println(result)
    
        bufferedReader.close()

# 2. 写 #

## FileWrite  ##

import java.io.{File, FileWriter}
    
    object TestWrite {
      def main(args: Array[String]): Unit = {
        val file = new File("d://data//out.txt")
        var fileWriter = new FileWriter(file)
    
        val source = Source.fromFile("d://data//word.txt")
        val lineIterator = source.getLines()
        while(lineIterator.hasNext){
          val line = lineIterator.next()
          fileWriter.write(line+"\n")
          fileWriter.flush()
        }
        fileWriter.close()
        source.close()
      }
    }

## PrintWriter  ##

import java.io.{File,PrintWriter}
    
        val file = new File("d://data//out.txt")
        val out = new PrintWriter(file)
    
        val source = Source.fromFile("d://data//word.txt")
        val lineIterator = source.getLines()
        while (lineIterator.hasNext) {
          val line = lineIterator.next()
          out.write(line + "\n")
          out.flush()
        }
        out.close()
        source.close()

## RandomAccessFile ##

val file = new File("d://data//out.log")
        val accessFile = new RandomAccessFile(file,"rw")    // r 读,w 写
        accessFile.seek(accessFile.length())                // 指向文件末尾
    
        val source = Source.fromFile("d://data//word.txt")
        val lineIterator = source.getLines()
        while (lineIterator.hasNext) {
          val line = lineIterator.next()
          accessFile.write(line.getBytes())
          accessFile.write('\n')
        }
        accessFile.close()
        source.close()

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpbmdlaW8_size_16_color_FFFFFF_t_70]: /images/20210923/403059bd6f7a41a5aef4d4ee66c52979.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpbmdlaW8_size_16_color_FFFFFF_t_70 1]: /images/20210923/40df90c840fc43ea86c3260b3f6b7105.png