How can I format a String number to have commas and round?

问题

What is the best way to format the following number that is given to me as a String?

String number = \"1000500000.574\" //assume my value will always be a String

I want this to be a String with the value: 1,000,500,000.57

How can I format it as such?

回答1:

You might want to look at the DecimalFormat class; it supports different locales (eg: in some countries that would get formatted as 1.000.500.000,57 instead).

You also need to convert that string into a number, this can be done with:

double amount = Double.parseDouble(number);

Code sample:

String number = "1000500000.574";
double amount = Double.parseDouble(number);
DecimalFormat formatter = new DecimalFormat("#,###.00");

System.out.println(formatter.format(amount));

回答2:

This can also be accomplished using String.format(), which may be easier and/or more flexible if you are formatting multiple numbers in one string.

    String number = "1000500000.574";
    Double numParsed = Double.parseDouble(number);

    System.out.println(String.format("The input number is: %,.2f", numParsed));
    // Or
    String numString = String.format("%,.2f", numParsed);

For the format string "%,.2f" - "," means separate digit groups with commas, and ".2" means round to two places after the decimal.

For reference on other formatting options, see https://docs.oracle.com/javase/tutorial/java/data/numberformat.html

回答3:

Once you've converted your String to a number, you can use

// format the number for the default locale
NumberFormat.getInstance().format(num)

// format the number for a particular locale
NumberFormat.getInstance(locale).format(num)

回答4:

I've created my own formatting utility. Which is extremely fast at processing the formatting along with giving you many features :)

It supports:

Comma Formatting E.g. 1234567 becomes 1,234,567.
Prefixing with "Thousand(K),Million(M),Billion(B),Trillion(T)".
Precision of 0 through 15.
Precision re-sizing (Means if you want 6 digit precision, but only have 3 available digits it forces it to 3).
Prefix lowering (Means if the prefix you choose is too large it lowers it to a more suitable prefix).

The code can be found here. You call it like this:

public static void main(String[])
{
   int settings = ValueFormat.COMMAS | ValueFormat.PRECISION(2) | ValueFormat.MILLIONS;
   String formatted = ValueFormat.format(1234567, settings);
}

I should also point out this doesn't handle decimal support, but is very useful for integer values. The above example would show "1.23M" as the output. I could probably add decimal support maybe, but didn't see too much use for it since then I might as well merge this into a BigInteger type of class that handles compressed char[] arrays for math computations.

回答5:

Given this is the number one Google result for format number commas java, here's an answer that works for people who are working with whole numbers and don't care about decimals.

String.format("%,d", 2000000)

outputs:

2,000,000

回答6:

public void convert(int s)
{
    System.out.println(NumberFormat.getNumberInstance(Locale.US).format(s));
}

public static void main(String args[])
{
    LocalEx n=new LocalEx();
    n.convert(10000);
}

回答7:

you can also use below solution -

public static String getRoundOffValue(double value){

        DecimalFormat df = new DecimalFormat("##,##,##,##,##,##,##0.00");
        return df.format(value);
}

回答8:

You can do the entire conversion in one line, using the following code:

String number = "1000500000.574";
String convertedString = new DecimalFormat("#,###.##").format(Double.parseDouble(number));

The last two # signs in the DecimalFormat constructor can also be 0s. Either way works.

回答9:

Here is the simplest way to get there:

String number = "10987655.876";
double result = Double.parseDouble(number);
System.out.println(String.format("%,.2f",result));

output: 10,987,655.88

回答10:

The first answer works very well, but for ZERO / 0 it will format as .00

Hence the format #,##0.00 is working well for me. Always test different numbers such as 0 / 100 / 2334.30 and negative numbers before deploying to production system.

来源：https://stackoverflow.com/questions/3672731/how-can-i-format-a-string-number-to-have-commas-and-round

标签

java

string

numbers

decimal

number-formatting