Reading and Writing Files in Kotlin - Different ways

There are multiple ways of reading and writing a text file, this is required while dealing with many applications.

 

  

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Here are some of the many ways of reading files in Kotlin:

1. Read a file using BufferedReader

import kotlin.Throws
import kotlin.jvm.JvmStatic
import java.io.BufferedReader
import java.io.File
import java.io.FileReader
import java.lang.Exception

object ReadFile {
    @Throws(Exception::class)
    @JvmStatic
    fun main(args: Array<String>) {
        // We need to provide file path as the parameter:
        val file = File("/home/user/Desktop/sample.txt")
        val br = BufferedReader(FileReader(file))
        var st: String?
        while (br.readLine().also { st = it } != null) println(st)
    }
}

2. Read a file using FileReader

import java.io.FileReader

object ReadingFromFile {
    @Throws(Exception::class)
    @JvmStatic
    fun main(args: Array<String>) {
        // pass the path to the file as a parameter
        val fr = FileReader("/home/user/Desktop/sample.txt")
        var i: Int
        while (fr.read().also { i = it } != -1) print(i.toChar())
    }
}

3. Read a file using Scanner Class

import java.io.File
import java.util.*

object ReadFromFileUsingScanner {
    @Throws(Exception::class)
    @JvmStatic
    fun main(args: Array<String>) {
        // pass the path to the file as a parameter
        val file = File("/home/user/Desktop/sample.txt")
        val sc = Scanner(file)
        while (sc.hasNextLine()) println(sc.nextLine())
    }
}

 

4. Using Stream- Read file line by line

import java.io.IOException
import java.nio.file.Files
import java.nio.file.Paths

object TestReadFile {
    @JvmStatic
    fun main(args: Array<String>) {
        try {
            Files.lines(Paths.get("/home/user/Desktop/sample.txt")).use { stream ->
                stream.forEach { x: String? ->
                    println(
                        x
                    )
                }
            }
        } catch (e: IOException) {
            e.printStackTrace()
        }
    }
}

Here are some of the many ways of writing files in Kotlin:

1. Write a file using FileWriter

import java.io.*
object WriteFile {
    /**
     * This class shows how to write file in Kotlin
     * @param args
     * @throws IOException
     */
    @JvmStatic
    fun main(args: Array<String>) {
        val data = "I am writing this String to File in Kotlin"
        writeUsingFileWriter(data)
        println("Done")
           }
      /**
     * Use FileWriter when number of write operations are less
     * @param data
     */
    private fun writeUsingFileWriter(data: String) {
        val file = File("/home/user/Desktop/sample.txt")
        var fr: FileWriter? = null
        try {
            fr = FileWriter(file)
            fr.write(data)
        } catch (e: IOException) {
            e.printStackTrace()
        } finally {
            //close resources
            try {
                fr!!.close()
            } catch (e: IOException) {
                e.printStackTrace()
            }
        }
    }
}

2. Write a file using BufferedWriter

import java.io.BufferedWriter
import java.io.File
import java.io.FileWriter
import java.io.IOException

object WriteFile {
    /**
     * This class shows how to write file in Kotlin
     * @param args
     * @throws IOException
     */
    @JvmStatic
    fun main(args: Array<String>) {
        val data = "I am writing this String to File in Kotlin"
        writeUsingBufferedWriter(data,3)
        println("Done")
    }

    /**
     * Use BufferedWriter when number of write operations are more
     * It uses internal buffer to reduce real IO operations and saves time
     * @param data
     * @param noOfLines
     */
    private fun writeUsingBufferedWriter(data: String, noOfLines: Int) {
        val file = File("/home/user/Desktop/sample.txt")
        var fr: FileWriter? = null
        var br: BufferedWriter? = null
        val dataWithNewLine = data + System.getProperty("line.separator")
        try {
            fr = FileWriter(file)
            br = BufferedWriter(fr)
            for (i in noOfLines downTo 1) {
                br.write(dataWithNewLine)
            }
        } catch (e: IOException) {
            e.printStackTrace()
        } finally {
            try {
                br!!.close()
                fr!!.close()
            } catch (e: IOException) {
                e.printStackTrace()
            }
        }
    }
}

3.Write a file using FileOutputStream

import java.io.File
import java.io.FileOutputStream
import java.io.IOException
import java.io.OutputStream


object WriteFile {
    /**
     * This class shows how to write file in Kotlin
     * @param args
     * @throws IOException
     */
    @JvmStatic
    fun main(args: Array<String>) {
        val data = "I am writing this String to File in Kotlin"
        writeUsingOutputStream(data)
        println("Done")
    }

    /**
     * Use Streams when you are dealing with raw data
     * @param data
     */
    private fun writeUsingOutputStream(data: String) {
        var os: OutputStream? = null
        try {
            os = FileOutputStream(File("/home/user/Desktop/sample.txt"))
            os.write(data.toByteArray(), 0, data.length)
        } catch (e: IOException) {
            e.printStackTrace()
        } finally {
            try {
                os!!.close()
            } catch (e: IOException) {
                e.printStackTrace()
            }
        }
    }
    }

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• Reading and Writing Files in Kotlin - Different ways