Different ways to write to a file in Kotlin

Different ways to write to a file in Kotlin:

Kotlin provides different ways to write to a file as direct methods and as extension methods. In this post, I will show you examples of different methods on how to write content to a file.

Method 1: By using File.writeText and File.appendText:

File.writeText is defined in java.io.File and using this method we can directly write one string to a file. Below is the definition of this method:

fun File.writeText(
    str: String,
    char: Charset = Charsets.UTF_8)

Here, str is the string that we are writing to the file and char is the Charset we are using. This is an optional value and by default it takes UTF-8.

For example:

package com.company

import java.io.File

fun main() {
    val filePath = "/Users/cvc/IdeaProjects/KotlinSampleProgram/src/sample.txt"
    val givenStr = "Hello World !!"
    val file = File(filePath)

    file.writeText(givenStr)
}

Here,

filePath is the path of the file. Change it to your own file path
givenStr is the string we are writing to the file.
We created one File object with the file path and used writeText to write givenStr in that file.

It will write the below content to the file:

Hello World !!

Note that it replaces the content in the file. appendText is another method that can be used to append to the existing content of a file.

If I run the below code:

package com.company

import java.io.File

fun main() {
    val filePath = "/Users/cvc/IdeaProjects/KotlinSampleProgram/src/sample.txt"
    val givenStr = "Hello World !!"
    val file = File(filePath)

    file.writeText(givenStr)
    file.appendText(givenStr)
}

The file will hold the below content:

Hello World !!Hello World !!

Method 2: By using File.writeBytes():

writeBytes is another method that can be used to write an array of bytes to a file. This method is defined as below:

fun File.writeBytes(array: ByteArray)

It takes a ByteArray and writes that byte array to the file.

Below program shows how we can use this method:

package com.company

import java.io.File

fun main() {
    val filePath = "/Users/cvc/IdeaProjects/KotlinSampleProgram/src/sample.txt"
    val givenStr = "Hello World !!"
    val file = File(filePath)

    file.writeBytes(givenStr.toByteArray())
}

Here,

we are converting the string givenStr to a byte array using toByteArray() method and writing that in the file using writeBytes

It will add the below line to the file:

Hello World !!

It is not appending the content to the file. For that, we need to use appendBytes method.

Method 3: By using PrintWriter:

java.io.File PrintWriter can be used by printWriter() method provided in Kotlin. This method returns one PrintWriter instance. We can use use{} to handle it.

For example:

package com.company

import java.io.File

fun main() {
    val filePath = "/Users/cvc/IdeaProjects/KotlinSampleProgram/src/sample.txt"

    File(filePath).printWriter().use{
        file ->
        file.print('H')
        file.print("ello")
        file.println()
        file.println("World")
    }
}

It will print the below lines to the file:

Hello
World

Method 4: By using BufferedWriter:

Kotlin profiles another method called bufferedWriter that returns a new BufferedWriter object. We can use use{} on it to write different contents to a file.

For example:

package com.company

import java.io.File

fun main() {
    val filePath = "/Users/cvc/IdeaProjects/KotlinSampleProgram/src/sample.txt"

    File(filePath).bufferedWriter().use{
        file ->
        file.write("Hello ")
        file.write("World")
    }
}

It will print the below content to the file:

Hello World

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Different ways to write to a file in Kotlin