ZetCode

Java DateTimeFormatter

last modified October 26, 2022

In this article we show how to formate and parse datetime values in Java with DateTimeFormatter.

DateTimeFormatter class is used to format and parse modern Java API datetime values.

The DateTimeFormatter contains two basics methods: format and parse.

DateTimeFormatter common constants

DateTimeFormatter contains several common formatter constants such as BASIC_ISO_DATE or ISO_DATE_TIME.

com/zetcode/FormatterEx.java
package com.zetcode;

import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

public class FormatterEx {

    public static void main(String[] args) {

        var now = LocalDateTime.now();
        DateTimeFormatter dtf1 = DateTimeFormatter.BASIC_ISO_DATE;
        DateTimeFormatter dtf2 = DateTimeFormatter.ISO_DATE;
        DateTimeFormatter dtf3 = DateTimeFormatter.ISO_DATE_TIME;
        DateTimeFormatter dtf4 = DateTimeFormatter.ISO_WEEK_DATE;
        DateTimeFormatter dtf5 = DateTimeFormatter.ISO_ORDINAL_DATE;

        System.out.println(dtf1.format(now));
        System.out.println(dtf2.format(now));
        System.out.println(dtf3.format(now));
        System.out.println(dtf4.format(now));
        System.out.println(dtf5.format(now));
    }
}

The program formats the current datetime with five common formatter constants.

20221026
2022-10-26
2022-10-26T20:33:56.705430917
2022-W43-3
2022-299

DateTimeFormatter Instant

The Instant is an instantaneous point on the time-line. We format it with DateTimeFormatter.ISO_INSTANT.

com/zetcode/FormatterEx.java
package com.zetcode;

import java.time.Instant;
import java.time.format.DateTimeFormatter;

public class FormatterEx {

    public static void main(String[] args) {

        var now = Instant.now();
        var dtf = DateTimeFormatter.ISO_INSTANT;

        System.out.println(dtf.format(now));
    }
}

The program formats the current Instant value.

2022-10-26T18:42:14.117403659Z

DateTimeFormatter FormatStyle

We can format LocalDate values with FormatStyle.SHORT, FormatStyle.MEDIUM, FormatStyle.LONG, FormatStyle.FULL format styles.

com/zetcode/FormatterEx.java
package com.zetcode;

import java.time.LocalDate;
import java.time.format.DateTimeFormatter;
import java.time.format.FormatStyle;

public class FormatterEx {

    public static void main(String[] args) {

        var now = LocalDate.now();

        var dtf1 = DateTimeFormatter.ofLocalizedDate(FormatStyle.SHORT);
        var dtf2 = DateTimeFormatter.ofLocalizedDate(FormatStyle.MEDIUM);
        var dtf3 = DateTimeFormatter.ofLocalizedDate(FormatStyle.LONG);
        var dtf4 = DateTimeFormatter.ofLocalizedDate(FormatStyle.FULL);

        System.out.println(dtf1.format(now));
        System.out.println(dtf2.format(now));
        System.out.println(dtf3.format(now));
        System.out.println(dtf4.format(now));
    }
}

The program formats the current local date with the four format styles.

10/26/22
Oct 26, 2022
October 26, 2022
Wednesday, October 26, 2022

DateTimeFormatter.ofPattern

Custom formats can be defined with DateTimeFormatter.ofPattern.

com/zetcode/FormatterEx.java
package com.zetcode;

import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

public class FormatterEx {

    public static void main(String[] args) {

        var now = LocalDateTime.now();

        var dtf1 = DateTimeFormatter.ofPattern("yyyy-MM-dd");
        var dtf2 = DateTimeFormatter.ofPattern("E, MMM dd yyyy");
        var dtf3 = DateTimeFormatter.ofPattern("EEEE, MMM dd, yyyy HH:mm:ss a");

        System.out.println(dtf1.format(now));
        System.out.println(dtf2.format(now));
        System.out.println(dtf3.format(now));
    }
}

The program prints the current local datetime with three custom formats.

2022-10-26
Wed, Oct 26 2022
Wednesday, Oct 26, 2022 21:01:49 PM

DateTimeFormatter localized custom formats

The next example creates localized datetime formats with ofPattern and Locale.

com/zetcode/FormatterEx.java
package com.zetcode;

import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.util.Locale;

public class FormatterEx {

    public static void main(String[] args) {

        var now = LocalDateTime.now();

        String pattern = "EEEE, MMM dd, yyyy HH:mm:ss a";
        var dtf1 = DateTimeFormatter.ofPattern(pattern, Locale.CHINA);
        var dtf2 = DateTimeFormatter.ofPattern(pattern, new Locale("RU", "ru"));
        var dtf3 = DateTimeFormatter.ofPattern(pattern, new Locale("SK", "sk"));

        System.out.println(dtf1.format(now));
        System.out.println(dtf2.format(now));
        System.out.println(dtf3.format(now));
    }
}

The program prints the current local datetime in Chinese, Russian, and Slovak.

星期三, 10月 26, 2022 21:07:17 下午
среда, окт. 26, 2022 21:07:17 PM
streda, okt 26, 2022 21:07:17 PM

Java DateTimeFormatterBuilder

Complex formatters can be generated with DateTimeFormatterBuilder.

com/zetcode/FormatterEx.java
package com.zetcode;

import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.time.format.DateTimeFormatterBuilder;
import java.time.temporal.ChronoField;
import java.util.Locale;

public class FormatterEx {

    public static void main(String[] args) {

        var now = LocalDateTime.now();

        DateTimeFormatter dtf = new DateTimeFormatterBuilder()
                .appendText(ChronoField.DAY_OF_MONTH)
                .appendLiteral(". ")
                .appendText(ChronoField.MONTH_OF_YEAR)
                .appendLiteral(" ")
                .appendText(ChronoField.YEAR)
                .parseCaseInsensitive()
                .toFormatter(new Locale("SK", "sk"));

        System.out.println(dtf.format(now));
    }
}

The program generates a formatter with DateTimeFormatterBuilder.

26. októbra 2022

DateTimeFormatter parse

The parse method fully parses the text producing a temporal object.

com/zetcode/FormatterEx.java
package com.zetcode;

import java.time.LocalDate;
import java.time.format.DateTimeFormatter;
import java.time.temporal.TemporalAccessor;

public class FormatterEx {

    public static void main(String[] args) {

        var d = "2022-10-26";

        DateTimeFormatter dtf = DateTimeFormatter.ISO_DATE;
        TemporalAccessor ta = dtf.parse(d);
        var ld = LocalDate.from(ta);
        System.out.println(ld);
    }
}

The program parses a string to produce a LocalDate value.

In this article, we have used DateTimeFormatter to format and parse datetime values.

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