Java example source code file (key_instant.xml)
The key_instant.xml Java example source code<?xml version="1.0" encoding="ISO-8859-1"?> <document> <properties> <title>Java date and time API - Instant <author>Stephen Colebourne </properties> <body> <section name="Instant"> <p> The most frequently used concept in Joda-Time is that of the <i>instant. An Instant is defined as <i>an instant in the datetime continuum specified as a number of milliseconds from 1970-01-01T00:00Z</i>. This definition of milliseconds is consistent with that of the JDK in <code>Date or <code>Calendar. Interoperating between the two APIs is thus simple. </p> <p> The millisecond instant can be converted to any date time field using a <a href="key_chronology.html">Chronology. To assist with this, methods are provided on <code>DateTime that act as getters for the most common date and time fields. More powerful access to the field can be obtained via its property. <source> DateTime dt = new DateTime(); // current time int month = dt.getMonth(); // gets the current month int month = dt.month().get(); // alternative way to get value String monthStr = dt.month().getAsText(); // gets the month name </source> </p> <p> To deal with local times (no time zone), or with date only or time only concepts, you should use the <a href="key_partial.html">partial classes. </p> </section> <section name="Using Instants in Joda-Time"> <p> Within Joda-Time an instant is represented by the <a href="apidocs/org/joda/time/ReadableInstant.html">ReadableInstant interface. There are four implementations of the interface provided: <ul> <li>Instant - A simple immutable implementation which is restricted to the UTC time zone and is intended for time zone and calendar neutral data transfer</li> <li>DateTime - The most commonly used class in the library, and an immutable representation of a date and time with calendar and time zone</li> <li>MutableDateTime - A mutable representation of date and time with calendar and time zone</li> <li>DateMidnight - A deprecated implementation, similar to <code>DateTime but with the time component forced to be midnight (at the start of a day)</li> </ul> We recommend the immutable implementations for general usage. </p> <p> The code can be used in various ways: <source> // setup date object for midday on Christmas 2004 (ISO year 2004) DateTime dt = new DateTime(2004, 12, 25, 12, 0, 0, 0); // get the year, 2004 int year = dt.getYear(); // get the day of week index 1 (Monday) to 7 (Sunday) int dow = dt.getDayOfWeek(); // get the text, such as 'Tuesday' String dowStr = dt.dayOfWeek().getAsText(); </source> Compared to <code>GregorianCalendar Joda-Time classes use 1-12 for months, and are immutable in the standard implementations. It is also easy to convert to and from the JDK classes. <source> // construct DateTime from JDK Date Date jdkDate = new Date(); DateTime dt = new DateTime(jdkDate); // construct Calendar from DateTime (could also construct a Date) GregorianCalendar cal = dt.toGregorianCalendar(); </source> </p> <p> Note that the interface <code>ReadableInstant should not be used like the collections API. The interface only contains the core subset of the operations of <code>DateTime. You should use the interface only when you feel the need to be flexible about future changes to the object passed into a method. You might also want to consider the <a href="apidocs/org/joda/time/ReadableDateTime.html">ReadableDateTime interface which extends <code>ReadableInstant to provide additional methods. </p> <subsection name="Nulls"> <p> Joda-Time defines a null instant as the current time. Thus, when a method is defined as taking a <code>ReadableInstant, passing null in will be the same as passing in an instant set to the current time. </p> </subsection> </section> </body> </document> Other Java examples (source code examples)Here is a short list of links related to this Java key_instant.xml source code file: |
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