Kotlin has inherited Java's fidgety (but very flexible) way of doing I/O, but with some simplifying extra features. We won't get into all of it here, so for starters, this is how to iterate through all the lines of a file (you'll need import java.io.File):

Kotlin has inherited Java's fidgety (but very flexible) way of doing I/O, but with some simplifying extra features. We won't get into all of it here, so for starters, this is how to iterate through all the lines of a file (you'll need import java.io.File):

fun File.writeText( text: String, charset: Charset = Charsets.UTF_8 ) fun File.writeBytes(array: ByteArray) fun File.printWriter( charset: Charset = Charsets.UTF_8 ): PrintWriter fun File.bufferedWriter( charset: Charset = Charsets.UTF_8, bufferSize: Int = DEFAULT_BUFFER_SIZE ): BufferedWriter · See the Kotlin java.io.File documentation for more information about the methods shown.

February 2, 2026 - For large files, Kotlin's sequence-based approach with useLines() processes files line by line without loading everything into memory.

FileSystem provides basic operations for working with files and directories, which are represented by yet another class under the same package - Path. ... kotlinx-io-core - provides IO primitives (Buffer, Source, Sink), filesystems support, depends on kotlinx-io-bytestring.

February 13, 2024 - private void copyDatabase(Context context, String dbName) { File dbPath = context.getDatabasePath(dbName); if (dbPath.exists()) { return; } dbPath.getParentFile().mkdirs(); try { final InputStream inputStream = context.getAssets().open("databases/" + dbName); final OutputStream output = new FileOutputStream(dbPath); byte[] buffer = new byte[8192]; int length; while ((length = inputStream.read(buffer, 0, 8192)) > 0) { output.write(buffer, 0, length); } output.flush(); output.close(); inputStream.close(); } catch (IOException e) { Log.d(TAG, "Failed to open file", e); e.printStackTrace(); } } This method will read the db file from assets and write it to the application database folder. This is the code I got after auto-conversion to Kotlin

Learn how to perform basic and advanced file operations in Kotlin including reading, writing, and manipulating files and directories.

January 21, 2025 - Before diving into the code, ensure your Kotlin project is configured correctly. You’ll often need to work with classes like BufferedReader or InputStream from Java. To get started, include import java.io.* in your file.

In this Kotlin File Operations tutorial, we demonstrated how to read the contents of a file using the readText() method of the File class from the java.io package, complete with a practical example.

June 13, 2026 - A: Use Kotlin Coroutines or Java's ExecutorService to perform file operations in background threads. This prevents the UI from freezing and ensures a smooth user experience. For example, use withContext(Dispatchers.IO) within a coroutine to ...

April 28, 2026 - In this quick tutorial, we’ll learn about various ways of writing content into a file using Kotlin extension methods – available in its standard library. Kotlin provides various ways of writing into a file in the form of extension methods for java.io.File.

November 16, 2020 - I worked out how to do basic string file input and output for Kotlin Native using their standard POSIX libraries. The code for these methods is at the bottom. This article explores it in more detail if you are interested.

June 8, 2022 - First, when I started working on Android and Java applications, using Java IO classes to write/read files to/from storage seemed so strange and confusing. In this tutorial, I focus on showing Java IO concepts, Kotlin extensions that make working with them easier and answering common questions about using them on Android.

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April 28, 2026 - In this quick tutorial, we’ll learn about the various ways of reading a file in Kotlin.

Learn how to write data to files in Kotlin using various approaches and best practices

November 4, 2025 - public static String loadCharacterData(String uniqueFilename) { Context currentContext = AppContextReference.getApplicationContext(); File target = new File(currentContext.getFilesDir(), uniqueFilename); StringBuilder contentAccumulator = new StringBuilder(); try (BufferedReader reader = new BufferedReader(new FileReader(target))) { String nextLine; while ((nextLine = reader.readLine()) != null) { contentAccumulator.append(nextLine); // Note: No newline appended here, unlike Solution 1 } } catch (FileNotFoundException missing) { Logger.logError("IO_Reader", missing); } catch (IOException ioEx) { Logger.logError("IO_Reader", ioEx); } return contentAccumulator.toString(); } For Kotlin projects, built-in extension functions on the File class offer maximum brevity, especially for internal file paths.

July 23, 2025 - This piece of code simply takes all the text in the file and prints it on the console. Another way of reading file contents is by directly creating a reader of the file as we do in this code: ... import java.io.File fun main (args: Array<String>) ...

There are many ways to create a file, read and write in a file. We'll discuss some of them briefly. Generally in many write methods a file is created itself but we'll see a method to create a file. We'll use File class available in java.io ...