datetime - How to parse/format dates with LocalDateTime? (Java 8)

Java 8 added a new java.time API for working with dates and times (JSR 310).

I have date and time as string (e.g. "2014-04-08 12:30"). How can I obtain a LocalDateTime instance from the given string?

After I finished working with the LocalDateTime object: How can I then convert the LocalDateTime instance back to a string with the same format as shown above?

Answer

Parsing date and time

To create a LocalDateTime object from a string you can use the static LocalDateTime.parse() method. It takes a string and a DateTimeFormatter as parameter. The DateTimeFormatter is used to specify the date/time pattern.

String str = "1986-04-08 12:30";
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm");

LocalDateTime dateTime = LocalDateTime.parse(str, formatter);

Formatting date and time

To create a formatted string out a LocalDateTime object you can use the format() method.

DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm");
LocalDateTime dateTime = LocalDateTime.of(1986, Month.APRIL, 8, 12, 30);
String formattedDateTime = dateTime.format(formatter); // "1986-04-08 12:30"

Note that there are some commonly used date/time formats predefined as constants in DateTimeFormatter. For example: Using DateTimeFormatter.ISO_DATE_TIME to format the LocalDateTime instance from above would result in the string "1986-04-08T12:30:00".

The parse() and format() methods are available for all date/time related objects (e.g. LocalDate or ZonedDateTime)