Reading Files Character by Character in Kotlin

Welcome to this lesson on reading files with Kotlin. Building upon our foundational knowledge of handling text files in Kotlin, this lesson will guide you through reading files character by character using Kotlin's I/O operations. These methods are crucial for handling varying file sizes efficiently and managing memory use effectively. By the end of this lesson, you’ll be able to read entire files, specific portions, and process files in manageable chunks, granting you flexible control over text data processing.

Before we jump into reading files, let’s review the example file that we will work with:

Hi!
This file contains some sample example text to use to test how the read method works.
Let’s do some programming!

This file contains multiple lines of varied lengths.

In Kotlin, reading a file character by character involves utilizing FileReader in conjunction with Kotlin's use construct for resource management. The FileReader allows us to open a file and read its contents one character at a time, which is helpful for detailed text processing. Here is how to read a file completely, character by character, using a loop:

import java.io.FileReader
import java.nio.file.Paths

fun main() {
    val filePath = Paths.get("example.txt")

    FileReader(filePath.toFile()).use { reader ->
        var charInt: Int = 0

        println("Reading file character-by-character:")
        while (reader.read().also { charInt = it } != -1) {
            print(charInt.toChar())
        }
    }
}

With this approach, filePath.toFile() converts the Path object into a File object required by FileReader. The read() method reads a character from the file, returning its integer representation, which is then converted to a character using toChar(). The loop continues until all characters have been read. Using the use construct ensures that resources are closed automatically after operations, preventing potential file locks and freeing system resources.

The expected output is:

Hi!
This file contains some sample example text to use to test how the read method works.
Let's do some programming!

This technique is well-suited for situations where processing files one character at a time is necessary, providing an efficient way to manage resources during file manipulation in Kotlin.