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POJodaTime Chronology caching
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copied!<p>I have successfully written a new Chronology that represents my company's fiscal calendar, based off of JodaTime. I referred to the JodaTime source code quite a bit, to figure out what I needed to do. One of the things I noticed in the <code>BasicChronology</code> class was the use of the inner class <code>YearInfo</code> to cache the 'firstDayOfYearMillis' - the number of milliseconds since 1970-01-01 (ISO). Figuring that, if it was enough of a performance bottleneck that JodaTime was caching it, I should probably add it to my chronology too.<br> When I did so, though, I made some modifications. Specifically, I moved the <code>getYearInfo</code> method into the <code>YearInfo</code> inner class, as well as making it static. I also moved the array used to store the cached values into the inner class as well. Full definition of the modified class is like this: </p> <pre><code>/** * Caching class for first-day-of-year millis. * */ private static final class YearInfo { /** * Cache setup for first-day-of-year milliseconds. */ private static final int CACHE_SIZE = 1 << 10; private static final int CACHE_MASK = CACHE_SIZE - 1; private static transient final YearInfo[] YEAR_INFO_CACHE = new YearInfo[CACHE_SIZE]; /** * Storage variables for cache. */ private final int year; private final long firstDayMillis; private final boolean isLeapYear; /** * Create the stored year information. * * @param inYear The year to store info about. */ private YearInfo(final int inYear) { this.firstDayMillis = calculateFirstDayOfYearMillis(inYear); this.isLeapYear = calculateLeapYear(inYear); this.year = inYear; } /** * Get year information. * * @param year The given year. * * @return Year information. */ private static YearInfo getYearInfo(final int year) { YearInfo info = YEAR_INFO_CACHE[year & CACHE_MASK]; if (info == null || info.year != year) { info = new YearInfo(year); YEAR_INFO_CACHE[year & CACHE_MASK] = info; } return info; } } </code></pre> <p>My question is... What are the performance or design implications of my changes? I've already decided that my changes should be thread-safe (given answers about final member variables). But why was the original implementation done the way it was, and not like this? I get why most of the methods that are being used effectively staticly aren't (given subclasses of <code>BasicChronology</code>), but I'll admit that some of my OO design stuff is a little rusty (having spent the last two years using RPG).<br> So... thoughts?</p>

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