工厂方法模式

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。?