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Fast:

Number Format📈

Example 1:

    double num = 12345.678;

    NumberFormat f1 = new DecimalFormat("###,###,###.0");
    System.out.println(f1.format(num));
12,345.7

Example 2:

    double num = 12345.678;

    NumberFormat f2 = new DecimalFormat("000,000.000000");
    System.out.println(f2.format(num));
012,345.678000

Example 3:

    double num = 12345.678;

    NumberFormat f3 = new DecimalFormat("$#,###,###.##");
    System.out.println(f3.format(num));
$12,345.68

Formating Dates and Times⌚

Symbol Meaning Example
y Year 25,2025
M Month 2,02,Feb, February
d Day 7, 07
h Hour 8, 08
m Minutes 25
S Second 17
a a.m / p.m AM, PM
z Time zone name Central European, CET
Z Time Zone offset -600

Example 1:

    LocalDate date = LocalDate.now();
    LocalDateTime localDateTime = LocalDateTime.now();
    LocalTime localTime = LocalTime.now();

    System.out.println(date.format(DateTimeFormatter.ISO_LOCAL_DATE));
    System.out.println(localTime.format(DateTimeFormatter.ISO_LOCAL_TIME));
    System.out.println(localDateTime.format(DateTimeFormatter.ISO_LOCAL_DATE_TIME));
2025-05-26
11:02:20.8602558
2025-05-26T11:02:20.8602558

Example 2:

    var dt = LocalDateTime.of(2025, Month.DECEMBER, 14,19,6,14);
    var dtFm1 = DateTimeFormatter.ofPattern("dd.MM.yyyy. hh:mm:ss");
    System.out.println(dt.format(dtFm1));

    var dtFm2 = DateTimeFormatter.ofPattern("MMM-dd-yy HH:mm:ss");
    System.out.println(dt.format(dtFm2));

    var dtFm3 = DateTimeFormatter.ofPattern("MMMM-dd-yy hh:mm:ss a");
    System.out.println(dt.format(dtFm3));

    System.out.println(dtFm3.format(dt));
14.12.2025. 07:06:14
Dec-14-25 19:06:14
December-14-25 07:06:14 PM
December-14-25 07:06:14 PM

More Example:

    var f4 = DateTimeFormatter.ofPattern("'Date:' dd.MM.yy. '| Time:' hh:mm:ss");
    System.out.println(f4.format(dt));

    var f5 = DateTimeFormatter.ofPattern("MMM.dd.yyyy. 'at' HH'h'm'm'ss's'");
    System.out.println(f5.format(dt));
Date: 14.12.25. | Time: 07:06:14
Dec.14.2025. at 19h6m14s

Internationalization

What is localization?

  • you can make your program adaptable to multiple locales of geographic regions
  • this includes:
    • translating string to difference languages
    • outputting dates in the correct format
    • outputting numbers in the correct format
    • etc...

Example 1:

    Locale locale = Locale.getDefault();
    System.out.println(locale);
    
    System.out.println();
    System.out.println(Locale.ITALIAN);
    System.out.println(Locale.ITALY);
    System.out.println(new Locale("hi", "IN"));
en_US

it
it_IT
hi_IN

en is language (mandatory)
US country (optional)

  • Create Locale and change Default Local Code example in Demo2 class

Localizing Number

  • Difference countries have different conventions when it comes to number
  • Localization can help to display the number in the appropriate locale format
  • For this purpose we use NumberFormat factory methods

NumberFormat Factory Methods

Method Description
getInstance(), getInstance(Locale locale) Generate purpose formatter
getNumberInstance(), getNumberInstance(Locale locale) Same as getInstance
getCurrencyInstance(), getCurrencyInstance(Locale locale) For formatting monetary amount
getPercentInstant(), getPercentInstant(Locale locale) For formatting percentages
getIntegerInstance(),getIntegerInstance(Locale locale) Rounds decimal number before displaying
getCompactNumberInstance(),getInstance(Locale locale, Style s) return compact Number Formatter

Formatting Example:

        double myNum = 1234.568;

        var us = NumberFormat.getInstance(Locale.US);
        System.out.println(us.format(myNum));

        var it = NumberFormat.getInstance(Locale.ITALY);
        System.out.println(it.format(myNum));

        var ca = NumberFormat.getInstance(Locale.CANADA_FRENCH);
        System.out.println(ca.format(myNum));
1,234.568
1.234,568
1 234,568

Formatting Currencies

        //Formatting currencies
        double price = 12.3;

        var usCurrency = NumberFormat.getCurrencyInstance(Locale.US);
        System.out.println(usCurrency.format(price));

        var ukCurrency = NumberFormat.getCurrencyInstance(Locale.UK);
        System.out.println(ukCurrency.format(price));

        var gerCurrency = NumberFormat.getCurrencyInstance(Locale.GERMANY);
        System.out.println(gerCurrency.format(price));
$12.30
£12.30
12,30 €

Formatting percentages

        double discount = 0.151;

        var usDiscount = NumberFormat.getPercentInstance(Locale.US);
        System.out.println(usDiscount.format(discount));

        var gerDiscount = NumberFormat.getPercentInstance(Locale.GERMANY);
        System.out.println(gerDiscount.format(discount));
15%
15 %

Warning when parsing with number

private void parsingNumber() throws ParseException {
    String myNum = "15.72";
    var us = NumberFormat.getInstance(Locale.US);
    System.out.println(us.parse(myNum));
    // 15.72
    var fr = NumberFormat.getPercentInstance(Locale.FRANCE);
    System.out.println(fr.parse(myNum));
    // throws java.text.ParseException
    // (in France, decimal point is not a dot, but a comma)
}

private void parsingNumberWithCurrency() throws ParseException {
    String price = "$12,345.67";
    var us = NumberFormat.getInstance(Locale.US);
    double priceValue = (Double) us.parse(price);
    System.out.println(priceValue);
    // 12345.67
    // NOTE: if you use non-US like locale, the parsing will throw an exception
}

Using CompactNumberFormat (new In java 17)

Example:

        int comNumber  = 8_765_432;

        var us1 = NumberFormat.getCompactNumberInstance(Locale.US, NumberFormat.Style.SHORT);
        System.out.println(us1.format(comNumber));

        var us2 = NumberFormat.getCompactNumberInstance(Locale.US, NumberFormat.Style.LONG);
        System.out.println(us2.format(comNumber));

        var us3 = NumberFormat.getCompactNumberInstance(Locale.GERMANY, NumberFormat.Style.SHORT);
        System.out.println(us3.format(comNumber));

        var us4 = NumberFormat.getCompactNumberInstance(Locale.GERMANY, NumberFormat.Style.LONG);
        System.out.println(us4.format(comNumber));
9M
9 million
9 Mio.
9 Millionen

DateTimeFormatter Factory Methods

Method Description
ofLocalizadDate(FormatStyle dateStyle) For formatting dates
ofLocalizedTime(FormatStyle timeStyle) For Formatting Times
ofLocalizedDateTime(FormatStyle dateStyle,FormatStyle timeStyle) For formatting dates and times
ofLocalizedDateTime(FormatStyle dateTimeStyle) For formatting dates and times

Example:

        var dtf = DateTimeFormatter.ofLocalizedDate(FormatStyle.SHORT);
        var fr = new Locale("fr", "FR");
        var dt = LocalDateTime.of(2023, Month.SEPTEMBER, 14, 9, 14, 57);
        System.out.println(dtf.withLocale(fr).format(dt));

        var dtf2 = DateTimeFormatter.ofLocalizedDate(FormatStyle.LONG);
        var usCus = new Locale("us", "EN");
        System.out.println(dtf2.withLocale(usCus).format(dt));

        // displaying locale
        var hr = new Locale("hr", "HR");
        var priceDis = 4.32;
        System.out.println(hr.getDisplayLanguage(Locale.US));

        System.out.println(hr.getDisplayCountry(Locale.US));

        System.out.println(NumberFormat.getCurrencyInstance(hr).format(priceDis));
14/09/2023
2023 Sep 14
Croatian
Croatia
4,32 HRK

Localization Note:

  • required to construct a Locale is language and country