Best way to store multiple variables to a file.

I want to write 3 arrays to a file to load them back in my array. I am not really sure how to do this i can write a single string to a file and then display it with a toast but need it to work with an array. Thanks for any help

package com.example.readwrite import androidx.appcompat.app.AppCompatActivity import android.os.Bundle import android.os.Environment import android.view.View import android.widget.Button import android.widget.EditText import android.widget.Toast import java.io.* import java.util.* val fileName ="Data" internal var myExternalFile: File?=null private val filepath = "MyFileStorage" class MainActivity : AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main) Load() Write() } fun Load(){ // findViewById(R.id.editTextFile) as EditText val viewButton = findViewById(R.id.button_view) as Button viewButton.setOnClickListener(View.OnClickListener { myExternalFile = File(getExternalFilesDir(filepath), fileName) myExternalFile = File(getExternalFilesDir(filepath),fileName) if(fileName.toString()!=null && fileName.toString().trim()!=""){ var fileInputStream = FileInputStream(myExternalFile) var inputStreamReader: InputStreamReader = InputStreamReader(fileInputStream) val bufferedReader: BufferedReader = BufferedReader(inputStreamReader) val stringBuilder: StringBuilder = StringBuilder() var text: String? = null while ({ text = bufferedReader.readLine(); text }() != null) { stringBuilder.append(text) } fileInputStream.close() //Displaying data on EditText Toast.makeText(applicationContext,stringBuilder.toString(),Toast.LENGTH_SHORT).show() } }) } fun Write(){ val fileData = "This is what will be saved 4" val emotionType = arrayOf("Happy", "Sad", "Happy") val dateOfEmotion = arrayOf("01/01/2021", "02/01/2021","01/01/2021" ) val note = arrayOf("Really happy today", "Supper duper sad today","Could not be happier" ) myExternalFile = File(getExternalFilesDir(filepath), fileName) try { val fileOutPutStream = FileOutputStream(myExternalFile) fileOutPutStream.write(fileData.toString().toByteArray()) fileOutPutStream.close() } catch (e: IOException) { e.printStackTrace() } Toast.makeText(applicationContext,"data save", Toast.LENGTH_SHORT).show() } }