如何使用逗号和欧元符号将双精度格式设置为某些格式

Question

I have a variable:

private double classicpreis  = 2.5;

and I want to change it into something like this:

private double classicpreis  = 2,5 €;

I thought a comma would be possible with double but it didn't work. So how can I achieve that?

Edit

I want to output it to something like this:

2,50 €

Answer 1

You can write the number in your code as a string constant, and parse it to a double using the locale of your choice. But that Euro sign leads me to believe that you should not be using double at all, but rather a decimal class.

Answer 2

You can not change the language itself, inside the code you will always need to write the decimal point if you wish to declare double values.

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However there are multiple ways to print the value with comma instead of point, for example in the display the user of the application gets to see.

Therefore you should always use the current locale format , so for example if the user is in Germany then it should print comma . There are automated processes for this in the Java library, like seen here: How to format double value for a given locale and number of decimal places? or in an official tutorial by Oracle .

The class to use is NumberFormat or DecimalFormat , here is a small example:

Locale currentLocale = ...
NumberFormat numberFormatter = NumberFormat.getNumberInstance(currentLocale);

double value = 2.5;

String formattedValue = numberFormatter.format(value);
System.out.println("Formatted value is: " + value);

The output now changes depending on what you set for the currentLocale . Your current locale can be get with Locale.getDefault() but you can also directly choose locales from different regions, for example with the constants defined in Locale like Locale.GERMANY .

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You can also apply decimal patterns to create numbers like 1.004,34 . The pattern therefore is #,##0.00 and it can be used this way:

String pattern = "#,##0.00";
DecimalFormat decimalFormatter = (DecimalFormat) numberFormatter; // The one from above

decimalFormatter.applyPattern(pattern);

String formattedValue = decimalFormatter.format(value);

With the format pattern you can also add the € symbol, just add it to the pattern.

Answer 3

The most simple solution is to use NumberFormat.getCurrencyInstance(Locale) or NumberFormat.getCurrenyInstance() and let it do all the formatting.

Suppose you have

double preis = 2.5;

then you can for example do

Locale locale = Locale.GERMANY;
NumberFormat numberFormat = NumberFormat.getCurrencyInstance(locale);
String s = numberFormat.format(preis);

and you will get "2,50 €" .

Note that the formatting takes care for all the details (use of decimal comma or point, chosen currency symbol, currency before or after number, number of spaces between) depending on the Locale you use. Examples: For Locale.GERMANY you get "2,50 €" , for Locale.US you get "$2.50" , for Locale,UK you get "£2.50" .

Answer 4

Its running fine now. My working code looks like this:

public class Bestellterminal { 

private double Preis = 0;
private double classicpreis  = 2.50;

classic.addActionListener(new ActionListener() {

        public void actionPerformed(ActionEvent e) {

            Preis = Preis + classicpreis;       

            Locale currentlocale = Locale.GERMANY;
            NumberFormat numberFormatter = 
            NumberFormat.getCurrencyInstance(currentlocale);
            String classicpreisx = numberFormatter.format(classicpreis);
            String preisx = numberFormatter.format(Preis);



            JLabel.setText(String.valueOf("Summe: " + preisx));

            }});

}

Thanks guys for your awesome help.