????2??android?????????????
????1?????????
????App·??:packages/providers/CalendarProvider
???????:packages/providers/CalendarProvider/src/com/android/provider/calendar/CalendarDatabaseHelper.java
????????????
????private static CalendarDatabaseHelper sSingleton = null;     
????public static synchronized CalendarDatabaseHelper getInstance(Context context) { 
????if (sSingleton == null) { 
????sSingleton = new CalendarDatabaseHelper(context); 
????} 
????return sSingleton; 
????} 
??????????????????????2?е??????B.
????2.Collator??
???????:libcore/luni/src/main/java/com/ibm/icu4jni/text/Callator.java
????libcore/luni/src/main/java/com/ibm/icu4jni/text/RuleBasedCallator.java
????????????
????public static Collator getInstance(Locale locale) { 
????return new RuleBasedCollator(locale); 
????} 
????p;    
????RuleBasedCollator(Locale locale) { 
????m_collator_ = NativeCollation.openCollator(locale.toString()); 
????} 
????static native int openCollator(String locale); 
??????????????????????E????????????????
????3.Editable??
???????:frameworks/base/core/java/android/text/Editable.java
????private static Editable.Factory sInstance = new Editable.Factory(); 
????/**
????* Returns the standard Editable Factory.
????*/ 
????public static Editable.Factory getInstance() { 
????return sInstance; 
????} 
????????????????D????????
????4.AccessibilityManager??
???????:frameworks/base/core/java/android/view/accessibility/AccessibilityManager.java
????public static AccessibilityManager getInstance(Context context) { 
????synchronized (sInstanceSync) { 
????if (sInstance == null) { 
????sInstance = new AccessibilityManager(context); 
????} 
????} 
????return sInstance; 
????} 
?????????????C????á?
????android?????????????????????????????????????????????????????????ó??????????????android????????????????????????????