EventBus，
/**Conveniencesingletonforappsusingaprocess-wideEventBusinstance.*/
publicstaticEventBusgetDefault(){
EventBusinstance=defaultInstance;
if(instance==null){
synchronized(EventBus.class){
instance=EventBus.defaultInstance;
if(instance==null){
instance=EventBus.defaultInstance=newEventBus();
}
}
}
returninstance;
}
                            

android源碼里面一大堆單例模式，比如下面這個(gè)實(shí)現(xiàn)方法：靜態(tài)方法加同步鎖
publicstaticWindowManagerGlobalgetInstance(){
synchronized(WindowManagerGlobal.class){
if(sDefaultWindowManager==null){
sDefaultWindowManager=newWindowManagerGlobal();
}
returnsDefaultWindowManager;
}
}