I want to format the number to String and fill 0 when it's not enough two characters
fun formatDuration(val duration):String {
val minutes = duration.toInt() / 60
return "$minutes"
}
For example, if minutes is 6， it should displayed 06 rather than 6.
You can padStart the toString() result of minutes.
I tried your code in the Kotlin Playground and it wasn't compilable / runnable. For the following example, I had to change parts of your fun:
fun main() {
println(formatDuration(364.34))
}
fun formatDuration(duration: Double): String {
val minutes = duration.toInt() / 60
// fill the result to be of 2 characters, use 0 as padding char
return minutes.toString().padStart(2, '0')
}
Executing this results in the output 06.
Alternatively, you can simply use String.format() from Java, just
return "%02d".format(minutes)
instead of return minutes.toString().padStart(2, '0'), the result stays the same.
You can achive this with padStart
Example:
val padWithSpace = "125".padStart(5)
println("'$padWithSpace'") // ' 125'
val padWithChar = "a".padStart(5, '.')
println("'$padWithChar'") // '....a'
// string is returned as is, when its length is greater than the specified
val noPadding = "abcde".padStart(3)
println("'$noPadding'") // 'abcde'
Related
I'm getting a price value from an API but it's a multi-digits decimal number like 0.4785835398457. I want to reduce this number to 3 or 4 digits number like 0.3234 and I'm showing that value in a TextView. So First, I have to form this value and second I need to convert it to String. I tried that DecimalFormat method like at onBindViewHolder part of my RecyclerAdapter.
override fun onBindViewHolder(holder: CoinListViewHolder, position: Int) {
val df = DecimalFormat("#.###")
df.roundingMode= RoundingMode.CEILING //<-----Here
df.format(coinList[position].price_usd.also { holder.itemView.coinPrice.text = it.toString() }) // <----- And here
holder.itemView.coinTicker.text= coinList[position].asset_id
holder.itemView.setOnClickListener {
listener.onItemClick(coinList, position)
}
But it did not work. Please help me.
Thanks in advance.
You can just use a string formatter that uses the number of decimal places you want:
val number = 123.12345
"%.3f".format(number).run(::println)
>> 123.123
That basically converts a float value (f) to a string, to three significant digits (.3). The format spec is here but it's a bit complex.
As far as your code goes, this:
df.format(coinList[position].price_usd.also { holder.itemView.coinPrice.text = it.toString() })
is equivalent to this:
val price = coinList[position].price_usd
holder.itemView.coinPrice.text = price.toString()
df.format(price)
I'm assuming you want to format the price and then display it in the TextView (right now you're just formatting it and doing nothing with the result), which would be this:
df.format(coinList[position].price_usd)
.let { holder.itemView.coinPrice.text = it.toString() }
i.e. do the format, and then do this with the result
Try holder.itemView.coinPrice.text = df.format(coinList[position].price_usd)
Im just working through some simple practice problems in kotlin. In my code below I'm taking a number and attempting to add the number members together. Ex. 29, return 2 + 9 = 11. There could be a better way to accomplish this but, I'm taking the numbers, converting to string, and then putting them into a list, ie ["2","9"] when I attempt to convert list[0].toInt() it returns 50. It appears there is some rounding taking place but I have not found another kotlin method to work with. Can anyone offer some insights? TIA
fun main(args: Array<String>) {
fun addTwoDigits(n: Int): Int {
val sliced = n.toString().toList()
val int1 = sliced[0].toInt()
println(sliced[0]) //returns "2"
println(int1) // returns 50
return sliced[0].toInt() + sliced[1].toInt()
}
println(addTwoDigits(29))
}
Koltin Char.toString(), which you are using in line:
val int1 = sliced[0].toInt()
converts the character using the ASCII Code table.
You can simply add a toString() call before the toInt() call:
val int1 = sliced[0].toString().toInt()
I'm trying to find the simplest way to convert a digit (0..9) into the respective character '0'..'9' in Kotlin.
My initial attempt was to write the following code:
fun convertToCharacter() {
val number = 0
val character = number.toChar()
println(character)
}
Of course, after running, I quickly saw that this produces \u0000, and not '0' like I expected. Then, remembering from how to do this in Java, I modified the code to add '0', but then this would not compile.
fun convertToCharacter() {
val number = 0
val character = number.toChar() + '0'
println(character)
}
What is the appropriate way to convert a number into its respective character counterpart in Kotlin? Ideally, I'm trying to avoid pulling up the ASCII table to accomplish this (I know I can add 48 to the number since 48 -> '0' in ASCII).
val character = '0' + number
is the shortest way, given that the number is in range 0..9
Kotlin stdlib provides this function since 1.5.0.
fun Int.digitToChar(): Char
Returns the Char that represents this decimal digit. Throws an exception if this value is not in the range 0..9.
If this value is in 0..9, the decimal digit Char with code '0'.code + this is returned.
Example
println(5.digitToChar()) // 5
println(3.digitToChar(radix = 8)) // 3
println(10.digitToChar(radix = 16)) // A
println(20.digitToChar(radix = 36)) // K
Like you said, probably the easiest way to convert an Int to the Char representation of that same digit is to add 48 and call toChar():
val number = 3
val character = (number + 48).toChar()
println(character) // prints 3
If you don't want to have the magic 48 number in your program, you could first parse the number to a String and then use toCharArray()[0] to get the Char representation:
val number = 3
val character = number.toString().toCharArray()[0]
println(character) // prints 3
Edit: in the spirit of the attempt in your question, you can do math with '0'.toInt() and get the result you were expecting:
val number = 7
val character = (number + '0'.toInt()).toChar()
println(number) // prints 7
How about 0.toString() instead of 0.toChar() ? If you are specifically after single digits, then 0.toString()[0] will give you a Char type
You can use an extension like this:
fun Int.toReadableChar(): Char {
return ('0'.toInt() + this).toChar()
}
You can apply this to any other class you want :)
Example:
println(7.toReadableChar())
>> 7
I want to add commas or point every 3 digit in EditText input.
Example :
input : 1000. Output : 1.000
input : 11000. Output : 11.000
If you are on the JVM you can use
"%,d".format(input)
which gives 11,000 for input 11000. Replace , with any delimiter you require.
If you want to use predefined number formats, e.g. for the current locale, use:
java.text.NumberFormat.getIntegerInstance().format(input);
Be also sure to check the other format instances, e.g. getCurrencyInstance or getPercentInstance. Note that you can use NumberFormat also with other locales. Just pass them to the get*Instance-method.
Some of the second variant can also be found here: Converting Integer to String with comma for thousands
If you are using it via Javascript you may be interested in: How do I format numbers using JavaScript?
Based on Splitframe answer above, did a simplified version (without the var):
fun Int.formatDecimalSeparator(): String {
return toString()
.reversed()
.chunked(3)
.joinToString(",")
.reversed()
}
And added some tests:
#Test
fun whenFormatDecimal_thenReturnFormatted() {
mapOf(
1 to "1",
12 to "12",
123 to "123",
1234 to "1,234",
12345 to "12,345",
123456 to "123,456",
1234567 to "1,234,567",
12345678 to "12,345,678",
123456789 to "123,456,789",
1234567890 to "1,234,567,890",
).forEach { (test, expected) ->
val result = test.formatDecimalSeparator()
assertEquals(expected, result)
}
}
In my case is a KMM project, and we don't support other languages, so it does the job. A better solution I would say to create an expect Util class and each platform implement the formatter taking account of the user Locale, etc.
System.out.println(NumberFormat.getNumberInstance(Locale.US).format(35634646));
This is a simple way that able you to replace default separator with any characters:
val myNumber = NumberFormat.getNumberInstance(Locale.US)
.format(123456789)
.replace(",", "،")
I used this for a non JVM Kotlin environment:
fun formatDecimalSeperators(number :String) :String {
var index = 1
return number
.takeIf { it.length > 3 }
?.reversed()
?.map { if (index++ % 3 == 0) "$it," else it }
?.joinToString("")
?.reversed()
?.removePrefix(",")
?: number
}
You can also use #Roland answer in Android String Resources to format it:
<string name="answer_count">%,01d answers</string>
For a method without getting Locale, you can use an extension to convert your Int into a formatted String like this below :
fun Int.formatWithThousandComma(): String {
val result = StringBuilder()
val size = this.toString().length
return if (size > 3) {
for (i in size - 1 downTo 0) {
result.insert(0, this.toString()[i])
if ((i != size - 1) && i != 0 && (size - i) % 3 == 0)
result.insert(0, "\'")
}
result.toString()
} else
this.toString()
}
I was solving a problem on codeforces in which I had to sum up the digits of a big number (it can have up to 100k digits) and I'd have to repeat that process until there is only one digit left and count the number of times I did that and I came up with a working solution, however I'd like to know if some things could have been done in a more "Kotlin-ish like way", so given:
fun main(args: Array<String>) {
println(transform(readLine()!!))
}
fun transform(n: String): Int {
var count = 0
var sum : Int
var s = n
while(s.length > 1) {
sum = (0 until s.length).sumBy { s[it].toInt() - '0'.toInt() }
s = sum.toString()
count++
}
return count
}
sum = (0 until s.length).sumBy { s[it].toInt() - '0'.toInt() } is there a way to I guess map the sum of digits in the string to the sum variable, or in general a better approach than the one I used?
When converting a Char to an Int it converts it to the ASCII value so I had to add "-'0'.toInt()" is there a faster way (not that it's too much to write, asking out of curiosity)?
How to make the String n mutable without creating a new String s and manipulating it? Or is that the desired (and only) way?
P.S. I'm a beginner with Kotlin.
When converting a Char to an Int it converts it to the ASCII value so I had to add "-'0'.toInt()" is there a faster way (not that it's too much to write, asking out of curiosity)?
You can simply write s[it] - '0', because subtracting Chars in Kotlin already gives you an Int:
public class Char ... {
...
/** Subtracts the other Char value from this value resulting an Int. */
public operator fun minus(other: Char): Int
...
}
But why are looping over the indexes when you could loop over the Chars directly?
sum = s.sumBy { it - '0' }
This is a functional (and recursive) style to solve it:
private fun sum(num: String, count: Int) : Int {
return num
//digit to int
.map { "$it".toInt() }
//sum digits
.sum()
//sum to string
.toString()
//if sum's length is more than one, do it again with incremented count. Otherwise, return the current count
.let { if (it.length > 1) sum(it, count + 1) else count }
}
And you call it like this:
val number = "2937649827364918308623946..." //and so on
val count = sum(number, 0)
Hope it helps!