How to separate large numbers with spaces kotlin - android-studio

Question

I have a calculator app and I want it to show large numbers with spaces between them when users enter their input. Currently, they don't have spaces between them like this: 10000; 100000; 1000000. I want them to show like this: 10 000; 100 000; 1 000 000. The second one looks much neater.
Here is my code
class CalculatorActivity : AppCompatActivity() {
#Suppress("PrivatePropertyName")
private var DigitOnScreen = StringBuilder(12)
private var operation: Char = ' '
private var leftHandSide: Double = 0.0
private var rightHandSide: Double = 0.0
private lateinit var binding: ActivityCalculatorBinding
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = ActivityCalculatorBinding.inflate(layoutInflater)
setContentView(binding.root)
binding.resultId.text = "0"
initializeButtons()
}
private fun initializeButtons() {
functionalButtons()
operationalButtons()
numericalButtons()
}
/**
* This function initializes all of our numerical buttons from
* [0 - 9]
*/
private fun numericalButtons() {
binding.oneBtn.setOnClickListener {
appendToDigitOnScreen("1")
}
binding.twoBtn.setOnClickListener {
appendToDigitOnScreen("2")
}
binding.threeBtn.setOnClickListener {
appendToDigitOnScreen("3")
}
binding.fourBtn.setOnClickListener {
appendToDigitOnScreen("4")
}
binding.fiveBtn.setOnClickListener {
appendToDigitOnScreen("5")
}
binding.sixBtn.setOnClickListener {
appendToDigitOnScreen("6")
}
binding.sevenBtn.setOnClickListener {
appendToDigitOnScreen("7")
}
binding.eightBtn.setOnClickListener {
appendToDigitOnScreen("8")
}
binding.nineBtn.setOnClickListener {
appendToDigitOnScreen("9")
}
binding.zeroBtn.setOnClickListener {
appendToDigitOnScreen("0")
}
binding.dotBtn.setOnClickListener {
appendToDigitOnScreen(".")
}
}
/**
* Insert the button been clicked onto the screen so user can see
* inputs for the button clicked
*/
private fun appendToDigitOnScreen(digit: String) {
// Add each digit to our string builder
DigitOnScreen.append(digit)
// display it on the screen of our mobile app
binding.resultId.text = DigitOnScreen.toString()
}
/**
* Initialize the operation keys in our calculator like the
* addition key, subtraction key and the likes
*/
private fun operationalButtons() {
binding.additionBtn.setOnClickListener {
selectOperation('A')
}
binding.subtractBtn.setOnClickListener {
selectOperation('S')
}
binding.divideBtn.setOnClickListener {
selectOperation('D')
}
binding.multipyBtn.setOnClickListener {
selectOperation('M')
}
}
/**
* Function to assign operational sign to our math calculations
*/
private fun selectOperation(c: Char) {
operation = c
leftHandSide = DigitOnScreen.toString().toDouble()
DigitOnScreen.clear()
binding.resultId.text = "0"
}
/**
* Handles functional operations in out application like
* clear button, backspace button and the clear everything button
*/
private fun functionalButtons() {
binding.clearEverythingBtn.setOnClickListener {
DigitOnScreen.clear()
binding.resultId.text = "0"
}
binding.clearBtn.setOnClickListener {
if (DigitOnScreen.isEmpty()) {
return#setOnClickListener
} else {
clearDigit()
}
}
binding.backspaceBtn.setOnClickListener {
if (DigitOnScreen.isEmpty()) {
return#setOnClickListener
} else {
clearDigit()
}
}
binding.equalBtn.setOnClickListener {
performMathOperation()
}
}
/**
* This function performs our Math Operation which is then showed on the screen.
*/
private fun performMathOperation() {
rightHandSide = DigitOnScreen.toString().toDouble()
when (operation) {
'A' -> {
val sum = OperationsHelper.add(leftHandSide, rightHandSide)
binding.resultId.text = sum.toString()
DigitOnScreen.clear()
DigitOnScreen.append(sum)
}
'S' -> {
val subtract = OperationsHelper.subtract(leftHandSide, rightHandSide)
binding.resultId.text = subtract.toString()
DigitOnScreen.clear()
DigitOnScreen.append(subtract)
}
'M' -> {
val multiply = OperationsHelper.multiply(leftHandSide, rightHandSide)
binding.resultId.text = multiply.toString()
DigitOnScreen.clear()
DigitOnScreen.append(multiply)
}
'D' -> {
val divide = OperationsHelper.divide(leftHandSide, rightHandSide)
binding.resultId.text = divide.toString()
DigitOnScreen.clear()
DigitOnScreen.append(divide)
}
}
}
/**
* This function remove the last digit on the screen.
*/
private fun clearDigit() {
val length = DigitOnScreen.length
DigitOnScreen.deleteCharAt(length - 1)
if (length <= 0) {
binding.resultId.text = "0"
}else{
binding.resultId.text = DigitOnScreen.toString()
}
}

Answer 1

you can solve it like this for example :
val x = "10000000"
val s:StringBuilder = java.lang.StringBuilder("")
x.mapIndexed{ index, c ->
if ((index+1)%3 ==0){
s.append(" ")
}
s.append(c)
}
println(s)
you need to store the value of all digts -> and every 3 digit make a space