Java Cookbook, 3rd Edition

Chapter 6. Dates and Times—New API

Introduction

Developers suffered for a decade and a half under the inconsistencies and ambiguities of the Date class from Java 1.0 and its replacement-wannabe, the Calendar class from Java 1.1. Several alternative "Date replacement” packages emerged, including the simple and sensible Date4J and the more comprehensive Joda-Time package. Java 8 introduced a new, consistent, and well-thought-out package for date and time handling, under the aegis of the Java Community Process, JSR-310, shepherded by Stephen Colbourne, based on his earlier package Joda-Time, but with several important design changes.^[26] This package is biased toward “ISO 8601” dates; the default format is, for example, 2015-10-23T10:22:45. But it can, of course, work with other calendar schemes.

One of the key benefits of the new API is that it provides useful operations such as adding/subtracting dates/times. Much time was wasted by developers using the previous APIs re-implementing these over and over. That said, millions of lines of code are based on the old APIs, so we review them briefly, and consider interfacing the new API to legacy code, in the final recipe of this chapter, Interfacing with Legacy Date and Calendar Classes.

Another advantage of the new API is that almost all objects are immutable, and thus thread-safe. This can be of considerable benefit as we move headlong into the massively parallel era.

Because there are no set methods, and thus the “get” method paradigm doesn’t ...