Read line and append something at the end - kotlin

Question

I'm new in kotlin. I'm trying to read file line by line and add something at the end to each of them.
My file before reading:
abcd;abcd;abcd;
bcda;bcda;bcda;
dacb;dacb;dacb;
My file after reading and appending:
abcd;abcd;abcd;smth1
bcda;bcda;bcda;smth2
dacb;dacb;dacb;smth3
I have code for reading file line by line but could you tell me how to add string to each of them?
val pathToFile = "abc.txt"
val scan = Scanner(File(pathToFile))
while (scan.hasNextLine()) {
val line = scan.nextLine()
var lista = ArrayList<String>()
lista = line.split(";") as ArrayList<String>
println(lista.get(0) + " and " + lista.get(1) + " and " + lista.get(2))
}

Answer 1

Januson has the right idea. Here is some Kotlin code to do the job:
inline fun File.mapLines(crossinline transform: (line: String) -> String) {
val tempFile = createTempFile(prefix = "transform", suffix = ".txt")
tempFile.printWriter().use { writer ->
this.forEachLine { line -> writer.println(transform(line)) }
}
check(this.delete() && tempFile.renameTo(this)) { "failed to replace file" }
}
Example usage:
val pathToFile = "abc.txt"
var index = 0
File(pathToFile).mapLines { line -> "${line}smth${++index}" }
If you are using Java 1.7+ then you can use Files.move instead of delete/renameTo:
Files.move(tempFile.toPath(), this.toPath(), StandardCopyOption.REPLACE_EXISTING)
See also Write to file after match in Kotlin.

Answer 2

You can't read and write to the same file unless you are using RandomAccessFile. Instead you should do the following:
Read line from your input file.
Do the modification you want (append to the end of the line, print line).
Write modified line to the output file.
After reading/writing all the data close both files.
Delete input file. Rename output file to the input file name.