Develop Reference

how do i restric a float value to only one placess after decimal in kotlin android

I have a number with some number decimal places,
How can i round this float number with one number decimal places
for example
1.366565646 convert to 1.3

In your case I think you need to trim the number not round it,
You can use this:
double d = 1.366565646;
DecimalFormat df = new DecimalFormat("#.#");
double p = Double.parseDouble(df.format(d));

Keep up to 3 decimals without doing any rounding

I have a double that I want to keep only 3 decimal places but without applying any rounding at all.
E.g. 92.36699 should be 92.366
I tried the following:
DecimalFormat nf= new DecimalFormat("#0.000");
String number = nf.format(originalNumber);
But this results in 92.367
How can I do what I need?

This isn't "no rounding", it's DOWN rounding. Simply set the roundingMode.
DecimalFormat nf = new DecimalFormat("#0.000");
nf.setRoundingMode(RoundingMode.DOWN);
String number = nf.format(originalNumber);
Note the difference between FLOOR and DOWN - only relevant for negative numbers. FLOOR rounds towards negative infinity therefore -92.36699 would become "-92.367".

Round Double value and exponential notation (java)

how to round "3.416436417734133 in "3.416436418" (nine positions after point) but also if i have "3.7578845854848E41" it round to "3.7578845855E41"? i'm trying to realyze a calculator..

You can use DecimalFormat, I am not sure about the other numbers but currently you have numbers which have single digit before the decimal point. So, check following example where you can format the double value. Note one more thing that you may need to change format pattern for your use case.
FOR EXAMPLE :
double d = 3.7578845854848E41;
double d2 = 3.416436417734133;
DecimalFormat f = new DecimalFormat("0.#########E0");
System.out.println(f.format(d));
System.out.println(f.format(d2));
OUTPUT :
3.757884585E41
3.416436418E0
//Replace E0 with space as format returns String
EDIT :
Because of your default locale. You can change local like this,
//Change locale
DecimalFormatSymbols decimalFormatSymbols = new DecimalFormatSymbols(Locale.US);
DecimalFormat f = new DecimalFormat("0.#########E0", decimalFormatSymbols);
//And than use decimal format

You may use BigDecimal to add a "scale" to your double value :
Double d = 3.416436417734133;
BigDecimal round = new BigDecimal(d);
round = round.setScale(9, BigDecimal.ROUND_CEILING);
System.out.println(round);

You can use this code.
BigDecimal aDecimal = new BigDecimal(3.416436417734133);
BigDecimal another = aDecimal.setScale(9, aDecimal.ROUND_HALF_UP);
System.out.println("another: " + another);
System.out.println(new BigDecimal(3.7578845854848E41,new
MathContext(11,RoundingMode.CEILING)));

Formatting a number with correct decimal scale

I need to format a number with scale of 2 decimal places. The original number may be a whole number or a number with three decimal places. However the result should be formatted to have commas and also two decimal places always regardless of whether the original number is whole number or having decimal places.
When original num = 56565656.342 ==> I need 56,565,656.34
When original num = 56565656 ==> I need 56,565,656.00
When original num = 56565656.7 ==> I need 56,565,656.70
I am using the following code which is formatting the code but its failing to add the two decimal places in the above 2 & 3 cases.
String originalNumber = "56565656.7";
BigDecimal b = new BigDecimal(originalNumber).setScale(2, BigDecimal.ROUND_HALF_UP);
String formattedNumber = NumberFormat.getInstance().format(b);
Please let me know if there is any way to accomplish this in efficeint way.
Thanks in advance.

Take a look at the DecimalFormat class.
Alternatively you can setScale method from the BigDecimal Class.
BigDecimal bg1 = new BigDecimal("56565656.342");
BigDecimal bg2 = new BigDecimal("56565656.00");
BigDecimal bg3 = new BigDecimal("56565656.70");
DecimalFormat df = new DecimalFormat("###,###.00");
System.out.println(df.format(bg1.doubleValue()));
System.out.println(df.format(bg2.doubleValue()));
System.out.println(df.format(bg3.doubleValue()));
System.out.println(bg1.setScale(2, BigDecimal.ROUND_HALF_UP));
System.out.println(bg2.setScale(2, BigDecimal.ROUND_HALF_UP));
System.out.println(bg3.setScale(2, BigDecimal.ROUND_HALF_UP));
Yields:
56,565,656.34
56,565,656.00
56,565,656.70
56565656.34
56565656.00
56565656.70
EDIT: Also forgot to mention: If you are after precision, I would recommend you use the setScale method, using the .doubleValue() method will yield a double which can cause loss of precision.

Just use NumberFormat and specify the fraction digits, and rounding method, to print :
String [] originalNumbers = new String[] {
"56565656.342",
"56565656.7",
"56565656"
};
NumberFormat df = NumberFormat.getInstance();
df.setMinimumFractionDigits(2);
df.setMaximumFractionDigits(2);
df.setRoundingMode(RoundingMode.HALF_UP);
for (String number : originalNumbers) {
String formattedNumber = df.format(new BigDecimal(number));
System.out.println(formattedNumber);
}
Will print
56,565,656.34
56,565,656.70
56,565,656.00
** Edit **
DecimalFormat df = new DecimalFormat("#,###.00");
Will produce the exact same result with the given code above.

DecimalFormat class would do it for you.... You will have to specify appropriate format.

DecimalFormat, how to set maximum number of integer digits via patern?

I want to format a number using DecimalFormat.
The maximum number of integer (and fractional) digits must be 2.
If the number is 345561.7301 the desired result would be: 61.73
This is my code:
double number = 345561.7301;
DecimalFormat formater =
(DecimalFormat)DecimalFormat.getInstance(Locale.US);//This locale only
formater.applyPattern("00.00");
System.out.println(formater.format(number));
I do not want to use setMaximumIntegerDigits() method.

What about just using substring?
double number = 345561.7301;
DecimalFormat formater =
(DecimalFormat)DecimalFormat.getInstance(Locale.US); //This locale only
formater.applyPattern("00.00");
//formater.setMaximumIntegerDigits(2); // <- don't want to use this
String tmp = formater.format(number);
System.out.println(tmp.substring(tmp.length() - 5));

Using a pattern might not be the best option in this scenario. I would reccommend using modulus division '%' and get the remainder of number/100.
double number = 345561.7301 % 100;
DecimalFormat formater = (DecimalFormat)DecimalFormat.getInstance(Locale.US);
formater.applyPattern("00.00");
System.out.println(formater.format(number));