Time Formatting Parsing in Java

Our first program will demonstrate time formatting and parsing in Java. Here’s the full source code:

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

public class TimeFormattingParsing {
    public static void main(String[] args) {
        // Here's a basic example of formatting a time
        // according to ISO_DATE_TIME, which is similar to RFC3339
        LocalDateTime now = LocalDateTime.now();
        System.out.println(now.format(DateTimeFormatter.ISO_DATE_TIME));

        // Time parsing uses the same formatter as formatting
        ZonedDateTime t1 = ZonedDateTime.parse("2012-11-01T22:08:41+00:00", DateTimeFormatter.ISO_DATE_TIME);
        System.out.println(t1);

        // You can also create custom formatters
        DateTimeFormatter customFormatter = DateTimeFormatter.ofPattern("h:mma");
        System.out.println(now.format(customFormatter));

        customFormatter = DateTimeFormatter.ofPattern("EEE MMM dd HH:mm:ss yyyy");
        System.out.println(now.format(customFormatter));

        customFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSSSSSX");
        System.out.println(ZonedDateTime.now().format(customFormatter));

        // Parsing with custom formatters
        String timeString = "8:41 PM";
        customFormatter = DateTimeFormatter.ofPattern("h:mm a");
        LocalDateTime t2 = LocalDateTime.parse(timeString, customFormatter);
        System.out.println(t2);

        // For purely numeric representations you can also use String.format
        // with the extracted components of the time value
        System.out.printf("%d-%02d-%02dT%02d:%02d:%02d-00:00%n",
                now.getYear(), now.getMonthValue(), now.getDayOfMonth(),
                now.getHour(), now.getMinute(), now.getSecond());

        // Parse will throw a DateTimeParseException on malformed input
        try {
            customFormatter = DateTimeFormatter.ofPattern("EEE MMM dd HH:mm:ss yyyy");
            LocalDateTime.parse("8:41PM", customFormatter);
        } catch (DateTimeParseException e) {
            System.out.println("Parsing error: " + e.getMessage());
        }
    }
}

This program demonstrates various ways to format and parse dates and times in Java using the java.time package, which was introduced in Java 8.

Here’s a breakdown of what the code does:

We start by formatting the current time using the ISO_DATE_TIME formatter, which is similar to RFC3339.
We then parse a specific date-time string using the same formatter.
We demonstrate how to create custom formatters using pattern strings. These patterns use specific letters to represent different parts of a date or time.
We show how to parse a time string using a custom formatter.
We use String.format to create a purely numeric representation of the current time.
Finally, we show how parsing can throw a DateTimeParseException when given malformed input.

To run this program, save it as TimeFormattingParsing.java, compile it with javac TimeFormattingParsing.java, and then run it with java TimeFormattingParsing.

The output will vary depending on the current time when you run it, but it will look something like this:

2023-06-15T10:30:15.123456
2012-11-01T22:08:41Z
10:30AM
Thu Jun 15 10:30:15 2023
2023-06-15T10:30:15.123456-07:00
0000-01-01T20:41
2023-06-15T10:30:15-00:00
Parsing error: Text '8:41PM' could not be parsed at index 0

This example showcases Java’s powerful date and time manipulation capabilities, which are more type-safe and less error-prone than the older java.util.Date and java.util.Calendar classes.

Epoch in Java

Random Numbers in Java

Learn X By Example

Title here

Time Formatting Parsing in Java