public static Calendar getInstance()
    {
        Calendar cal = createCalendar(TimeZone.getDefaultRef(), Locale.getDefault(Locale.Category.FORMAT));
        cal.sharedZone = true;
        return cal;
    }


  public static Calendar getInstance(TimeZone zone,
                                       Locale aLocale)
    {
        return createCalendar(zone, aLocale);
    }

    public static Calendar getInstance(TimeZone zone)
    {
        return createCalendar(zone, Locale.getDefault(Locale.Category.FORMAT));
    }

    public static Calendar getInstance(Locale aLocale)
    {
        Calendar cal = createCalendar(TimeZone.getDefaultRef(), aLocale);
        cal.sharedZone = true;
        return cal;
    }



    private static Calendar createCalendar(TimeZone zone,
                                           Locale aLocale)
    {
        Calendar cal = null;

        String caltype = aLocale.getUnicodeLocaleType("ca");
        if (caltype == null) {
            // Calendar type is not specified.
            // If the specified locale is a Thai locale,
            // returns a BuddhistCalendar instance.
            if ("th".equals(aLocale.getLanguage())
                    && ("TH".equals(aLocale.getCountry()))) {
                cal = new BuddhistCalendar(zone, aLocale);
            } else {
                cal = new GregorianCalendar(zone, aLocale);
            }
        } else if (caltype.equals("japanese")) {
            cal = new JapaneseImperialCalendar(zone, aLocale);
        } else if (caltype.equals("buddhist")) {
            cal = new BuddhistCalendar(zone, aLocale);
        } else {
            // Unsupported calendar type.
            // Use Gregorian calendar as a fallback.
            cal = new GregorianCalendar(zone, aLocale);
        }

        return cal;
    }

------解决方案--------------------
class A{
 private static A a=null;    //创建本对象的引用，私有，不可以直接调用
 private A(){}               //创建私有的构造方法，不可以直接调用初始化类
 public static A getA(){     //初始化类的方法
   if(a==null){              //如果a还没有初始化，就初始化该类
     a=new A();
   }
   return a;
 }  
}