Develop Reference

How to count the number of string characters in Kotlin?

#SuppressLint("SetTextI18n")
private fun countName(x: String) {
val textView: TextView = findViewById(R.id.result)
for (i in 0 until x.length) {
textView.text = i.toString()
}
}
This is what I have so far. It works somewhat but for some reason it is lagging behind 1 number. For example, if I type James, the number it will output would be 4.

How to get the number of characters in a string (usually what you want):
str.length
How to get the number of Unicode code points in a string (because sometimes a code point is encoded as multiple characters):
str.codePointCount(0, str.length)
See this Java answer for more details on the difference between these two options.

There are many simple ways to get the number of characters in a string. but if you want to know the mistake in your code you should have started to count from 1 instead of 0.
for (i in 1 until x.length) {
textView.text = i.toString()
}

kotlin - Problem with my if statement and operator

This is my goal : user click on minus button the amount decrease by one and there is a if statement to not allow the amount go lower than 0 .
This is my Code :
var number = 0
view.text_amount.visibility = View.GONE
view.plus_btn.setOnClickListener {
if (number == 5) {
Toast.makeText(
requireContext(),
"Limit in order",
Toast.LENGTH_SHORT
).show()
} else {
view.text_amount.visibility = View.VISIBLE
number++
view.text_amount.text = number.toString()
}
}
view.minus_btn.setOnClickListener {
if (number <= 0) {
view.text_amount.visibility = View.GONE
} else {
number--
view.text_amount.text = number.toString()
}
}
there is problem with code : I don't want the amount be visible after getting to 0 . it's better experience when the amount is equal to 0 not be visible .
I think it has a simple solution but I can't see it .
do you have any idea ?

Your code works fine! If you want to make it simpler, there's a bit of repeated logic you could condense into one function that handles the situations:
fun adjustValue(amount: Int) {
val adjusted = number + amount
if (adjusted > 5) // show Toast
number = adjusted.coerceIn(0, 5)
view.text_amount.text = number.toString()
view.text_amount.visibility = if (number == 0) View.GONE else View.VISIBLE
}
view.minus_btn.setOnClickListener { adjustValue(-1) }
view.plus_btn.setOnClickListener { adjustValue(1) }
basically the idea is you work out the new value (I'm using a temporary variable so we never set number to an invalid value) and show whatever warnings you need to. Then the coerceIn line makes sure we lock it within the valid range of allowed values.
You could do if/else checks and only set the new value if it's a valid one, but sometimes it's simpler and shorter to just set things and then worry about the edge cases, so this is just an example of that!
Same thing for the TextView bit - it's easier to just set the value whatever it is, and then set whether it should be displayed or not. You could use if/else branches to look at the value and decide whether to set the text or not... but why make your life hard? We know the value's in the valid 0 to 5 range, we can hide it if it's 0 and show it otherwise... easy!
You could make the function take a Boolean instead, like plus: Boolean and then go val adjusted = number + if (plus) 1 else -1, but making it an Int means you could easily add a +10 button or whatever without adding any more code or any more validation logic, and it's not any more complicated to pass in -1 instead of false (arguably it's clearer!)
that's probably more than you were asking for but hopefully it's useful. If nothing else, the "just set the text and the visibility every time" approach is good and neat

Decrease the value of text_amount only if it contains a value greater than 0 and after that check again its value and if it is 0 then hide it:
view.minus_btn.setOnClickListener {
if (number > 0) {
number--
view.text_amount.text = number.toString()
if (number == 0) view.text_amount.visibility = View.GONE
}
}

Kotlin check for words in string

I have a NSFW class that scans texts like item names and descriptions against a list of known NSFW-words.
That would be the best approach to test a list of strings like
let nsfw = listof(
"badword",
"curseword",
"ass",
... 200+ more
)
against a string like:
This is the text that contains a badword // returns true
Please note that i need to check for full words. not parts of words.
so the sentence:
The grass is grean // returns false
Because grass is not a bad word.
Ive tried something like this but it doesnt check for full words.
val result = nsfw.filter { it in sentence.toLowerCase() }

You may build a regex like
\b(?:word1|word2|word3...)\b
See the regex demo. Then, use it with the Regex.containsMatchIn method:
val nsfw = listOf(
"badword",
"curseword",
"ass"
)
val s1 = "This is the text that contains a badword"
val s2 = "The grass is grean"
val rx = Regex("\\b(?:${nsfw.joinToString(separator="|")})\\b")
println(rx.containsMatchIn(s1)) // => true
println(rx.containsMatchIn(s2)) // => false
See this Kotlin demo.
Here, nsfw.joinToString(separator="|") joins the words with a pipe (the alternation operator) and the "\\b(?:${nsfw.joinToString(separator="|")})\\b" creates the correct regex.
If your words may contain special regex metacharacters, like +, ?, (, ), etc., you need to "preprocess" the nsfw values with the Regex.escape method:
val rx = Regex("\\b(?:${nsfw.map{Regex.escape(it)}.joinToString("|")})\\b")
^^^^^^^^^^^^^^^^^^^^^^
See the Kotlin demo.
AND one more thing: if the keywords may start/end with chars other than letters, digits and underscores, you cannot rely on \b word boundaries. You may
Use whitespace boundaries: val rx = Regex("(?<!\\S)(?:${nsfw.map{Regex.escape(it)}.joinToString("|")})(?!\\S)")
Use unambiguous word boundaries: val rx = Regex("(?<!\\w)(?:${nsfw.map{Regex.escape(it)}.joinToString("|")})(?!\\w)")

You can use split() on the string that you want to check, with space as a delimiter, so you create a list of its words, although this does not always guarantee that all words will be extracted successfully, since there could exist other word separators like dots or commas etc. If that suits you, do this:
val nsfw = listOf(
"badword",
"curseword",
"ass"
)
val str = "This is the text that contains a badword"
val words = str.toLowerCase().split("\\s+".toRegex())
val containsBadWords = words.firstOrNull { it in nsfw } != null
println(containsBadWords)
will print
true
If you want a list of the "bad words":
val badWords = words.filter { it in nsfw }

Kotlin: SumbyDouble returning additional decimals

I am summing double value from arraylist its giving additional decimals as 99999, how to fix this, please guide
ex
class ExDet{var expName:String ="",var expAmount:Double = 0.0}
val arrayList = ArrayList<ExDet>()
arrayList.add(ExDet("Abc 1",45.66))
arrayList.add(ExDet("DEF 1",10.0))
arrayList.add(ExDet("Lee 1",600.89))
arrayList.add(ExDet("Ifr 1",200.9))
var amt = arrayList.sumByDouble{ it.expAmount }
Expected Value of Amount is :
Amt = 857.45
But it returns
Amt = 857.4499999
Sample Code to Test
data class ExDet(var expName:String ="" ,var expAmount:Double=0.0)
fun main(args: Array<String>) {
val arrayList = ArrayList<ExDet>()
arrayList.add(ExDet("Abc 1",45.66))
arrayList.add(ExDet("DEF 1",10.0))
arrayList.add(ExDet("Lee 1",600.89))
arrayList.add(ExDet("Ifr 1",200.9))
var amt = arrayList.sumByDouble{ it.expAmount }
println("Amount is : $amt")
}

The issue you are confronted with is that floating point numbers are build on top of base 2, not base 10.
Think how you can easily represent a third as a fraction (1/3), but when you convert to decimal you get a repeating (recurring) number after the radix point (i.e. 0.33...). Some decimal numbers are recurring when represented in base-2, e.g. x.9. The computer has a finite number of bits, so the (base-2) number is truncated. All the truncation errors can add up.
You need to round to the required precision (e.g. round(x * 100) / 100).
If you are only interested in how it is displayed then you can use the format function with something like "%.2f".
String.format("%.2f", value)

Check Value from mysql using android

I have a table which has a field called Sold , in that field i store 0 and 1.
So 1 means sold and 0 mean Available.
K, my problem is that ,I want to change 0 to available and 1 to sold when i diplay information into my emulator , here what i tried but it returning sold even though i have 0 in my database :
if (sold.length()==0){
Log.d("checking","Inside = 0");
val = "Available";}
else if (sold.length()>0)
Log.d("checking","Inside = 1");
val = "Sold
And sold contains a value from a database.
please help to change 0 to Available and 1 to Sold.

if(sold.equalIgnoreCase("0"))
{
Log.d("checking","Inside = 0");
}else
{
Log.d("checking","Inside = 1");
}

The sold.length you have there is the actual length of the String representation "sold" that you are using. Meaning that if you have the word "some" this .length() equals 4.
So in your snippet the sold variable is the "0" or "1" respectively so the sold.length() always equals to 1. Try to cast the String variable into an Integer and make the comparison or even better try to make the variable into Integer from the beginning.