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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)));

Java: displaying ONLY two decimal numbers

When I click calculate to display a calculation it displays the following answer:
Net Pay 31030.38076923077
How can I make it only display two decimal numbers after the dot. example $31030.38

Use DecimalFormat:
double f = 31030.38076923077;
DecimalFormat df = new DecimalFormat("#.00");
System.out.println(f+" "+df.format(f));

Use BigDecimal like this
double d = 31030.38474923077;
BigDecimal dec = new BigDecimal(d).setScale(2, RoundingMode.HALF_UP);
System.out.println(dec);

Rounding off double value in Java

Currently I'm using DecimalFormat class to round off double value
double d = 42.405;
DecimalFormat f = new DecimalFormat("##.00");
System.out.println(f.format(d));
output: 42.41;
I'm doing browser app testing using Selenium, so based on the browser I need to round off the value.
For Example:
IE rounds off 42.405 to 42.40 and others rounds off to 42.41. But if values are like 42.403, 42.406 then I see consistency across all browsers. So now I have to put a condition in my script so if browser is IE then round off should happen in such a way that I should get 42.40 and for other browsers is should get 42.41. How can i do this?

You can specify the RoundingMode for the DecimalFormatter, but please choose it as per your needs(I've just given an example using HALF_UP).
double d = 42.405;
DecimalFormat f = new DecimalFormat("##.00");
f.setRoundingMode(RoundingMode.HALF_UP);
System.out.println(f.format(d)); // Prints 42.41
Alternatively, you can also use BigDecimal(incase you know why we usually go for BigDecimal instead of double) for the same.
double d = 42.405;
BigDecimal bd = new BigDecimal(d);
bd = bd.setScale(2, RoundingMode.HALF_UP);
System.out.println(bd.doubleValue()); // Prints 42.41

DecimalFormat f=new DecimalFormat("0.00");
String formate = f.format(value);
double finalValue = (Double)f.parse(formate) ;
System.out.println(finalValue);

Use setRoundingMode as:
f.setRoundingMode( RoundingMode.DOWN );
How to round a number to n decimal places in Java

try this may be helpful:
double d = 42.405;
System.out.println(String.format("%2.2f", d));

Also you can do it "handly" as follow
double d = 42.405;
final double roundedValue = (Math.round(d * 100) / (double) 100);
In case of 42.405 you get 42.41 and in case of 42.404 - 42.4
And so after
System.out.println(String.format("%2.2f", roundedValue));
you will get necessary output. 42.41 or 42.40 correspondingly.

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.

Formatting double to 2 decimals doesn't work

I want to round this double:
3.499999999999999
to:
3.50
And I already used these two methods:
DecimalFormat df = new DecimalFormat("0.00");
double result = Double.valueOf(df.format(input));
System.out.println(answer);
and
public double round(double input)
{
int decimalPlace = 2;
BigDecimal bd = new BigDecimal(input);
bd = bd.setScale(decimalPlace,BigDecimal.ROUND_UP);
return (bd.doubleValue());
}
But It keeps printing:
3.5
Does anyone have a solution for this? Because I really think that this should work. Thanks for your help.

Your first solution is really, really close. Just do this:
DecimalFormat df = new DecimalFormat("0.00");
System.out.println(df.format(input));
The reason your version doesn't work is that you're taking the input double, formatting it as a String with 2dp, but then converting it back to a double. System.out.println is then printing the double as it always would, with no special decimal-place rules.

You can use the printf formatting which may be simpler.
System.out.printf("%.2f%n", 3.5);
prints
3.50

Did you try replacing the 0's with #'s?
DecimalFormat df = new DecimalFormat("#.##");
System.out.println(df.format(input));
According to here the # will be resolved to 0 if the digit is absent

You can use Precision class of apache commons-math
double result = Precision.round(3.499999999999999, 2);