工厂方法模式
2023-12-31 19:30:55
简单??模式
????????简单??模式指由?个??对象来创建实例,客户端不需要关注创建逻辑,只需提供传???的参数。
????????UML 类图如下:
????????适?于??类负责创建对象较少的情况,缺点是如果要增加新产品,就需要修改??类的判断逻辑,违背开闭原则,且产品多的话会使??类?较复杂。
????????Calendar 抽象类的 getInstance ?法,调? createCalendar ?法根据不同的地区参数创建不同的?历对象。
/**
* Gets a calendar using the default time zone and locale. The
* <code>Calendar</code> returned is based on the current time
* in the default time zone with the default
* {@link Locale.Category#FORMAT FORMAT} locale.
*
* @return a Calendar.
*/
public static Calendar getInstance()
{
return createCalendar(TimeZone.getDefault(), Locale.getDefault(Locale.Category.FORMAT));
}
/**
* Gets a calendar using the specified time zone and default locale.
* The <code>Calendar</code> returned is based on the current time
* in the given time zone with the default
* {@link Locale.Category#FORMAT FORMAT} locale.
*
* @param zone the time zone to use
* @return a Calendar.
*/
public static Calendar getInstance(TimeZone zone)
{
return createCalendar(zone, Locale.getDefault(Locale.Category.FORMAT));
}
/**
* Gets a calendar using the default time zone and specified locale.
* The <code>Calendar</code> returned is based on the current time
* in the default time zone with the given locale.
*
* @param aLocale the locale for the week data
* @return a Calendar.
*/
public static Calendar getInstance(Locale aLocale)
{
return createCalendar(TimeZone.getDefault(), aLocale);
}
/**
* Gets a calendar with the specified time zone and locale.
* The <code>Calendar</code> returned is based on the current time
* in the given time zone with the given locale.
*
* @param zone the time zone to use
* @param aLocale the locale for the week data
* @return a Calendar.
*/
public static Calendar getInstance(TimeZone zone, Locale aLocale)
{
return createCalendar(zone, aLocale);
}
private static Calendar createCalendar(TimeZone zone, Locale aLocale)
{
CalendarProvider provider =
LocaleProviderAdapter.getAdapter(CalendarProvider.class, aLocale)
.getCalendarProvider();
if (provider != null) {
try {
return provider.getInstance(zone, aLocale);
} catch (IllegalArgumentException iae) {
// fall back to the default instantiation
}
}
Calendar cal = null;
if (aLocale.hasExtensions()) {
String caltype = aLocale.getUnicodeLocaleType("ca");
if (caltype != null) {
switch (caltype) {
case "buddhist":
cal = new BuddhistCalendar(zone, aLocale);
break;
case "japanese":
cal = new JapaneseImperialCalendar(zone, aLocale);
break;
case "gregory":
cal = new GregorianCalendar(zone, aLocale);
break;
}
}
}
if (cal == null) {
// If no known calendar type is explicitly specified,
// perform the traditional way to create a Calendar:
// create a BuddhistCalendar for th_TH locale,
// a JapaneseImperialCalendar for ja_JP_JP locale, or
// a GregorianCalendar for any other locales.
// NOTE: The language, country and variant strings are interned.
if (aLocale.getLanguage() == "th" && aLocale.getCountry() == "TH") {
cal = new BuddhistCalendar(zone, aLocale);
} else if (aLocale.getVariant() == "JP" && aLocale.getLanguage() == "ja"
&& aLocale.getCountry() == "JP") {
cal = new JapaneseImperialCalendar(zone, aLocale);
} else {
cal = new GregorianCalendar(zone, aLocale);
}
}
return cal;
}
????????和简单??模式中??负责?产所有产品相?,???法模式将?成具体产品的任务分发给具体的产品??。
????????UML 类图如下:?
????????也就是定义?个抽象??,其定义了产品的?产接?,但不负责具体的产品,将?产任务交给不同的派?类??。这样不?通过指定类型来创建对象了。?
文章来源:https://blog.csdn.net/u010096526/article/details/135318199
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