Summary of Java Singleton patterns

The implementation of the Singleton mode is summarized as follows:

The first way: the method of obtaining the instance synchronously, multithreading security, lazy mode. Initialize at the moment the instance is invoked.

 Public classSingleton1 {Private StaticSingleton1 instance =NULL; PrivateSingleton1 () {} Public Static synchronizedSingleton1 getinstance () {if(Instance = =NULL) {instance=NewSingleton1 (); }        returninstance; }}

The first way: a hungry man mode, thread-safe, but slow loading. The object information was initialized at the moment the class was loaded.

 Public class Singleton2 {    //  class Loads the moment it creates a unique instance    privatestaticnew Singleton2 ();     Private Singleton2 () {    }    publicstatic  Singleton2 getinstance () {         return  instance;}    }

The Third way: Double check lock mode, only at the time of the first creation of the mutual exclusion check, empty to create the object.

 Public classSingleton3 {//the use of volatile after JDK 1.5 to initialize the instance ensures that multithreading is handled correctly    Private Static volatileSingleton3 instance =NULL; PrivateSingleton3 () {} Public StaticSingleton3 getinstance () {if(Instance = =NULL) {            synchronized(Singleton3.class) {                if(Instance = =NULL) {instance=NewSingleton3 (); }            }        }        returninstance; }}

Summary of Java Singleton patterns