Simple interest mode (a hungry man mode, lazy mode) thread safety and problem solving

Single-Case mode

1. A Hungry man mode: Create an instance when the class is loaded (thread-safe)

2. Lazy mode: Create an instance (thread unsafe) solution when the method is run: double-check

A Hungry man mode:

 Public classSingleton {//a hungry man mode//privatize a constructor    PrivateSingleton () {}//instantiating an object    Private StaticSingleton instance =NewSingleton (); //How to get an instance     Public StaticSingleton getinstance () {returninstance; }}

Lazy mode:

//Lazy Mode//privatize a constructor    PrivateSingleton () {}//instantiating an object    Private StaticSingleton instance; //How to get an instance     Public StaticSingleton getinstance () {if(Instance = =NULL) {instance=NewSingleton (); }        returninstance; }

Workaround 1 (slow)

// How to get an instance    synchronized  Public Static Singleton getinstance () {       ifnull) {           new  Singleton ();       }         return instance;    }

Workaround 2 (slow)

// How to get an instance      Public Static Singleton getinstance () {      synchronized (Singleton.  Class          ){ifnull) {              new  Singleton ();          }           return  instance;      }    }

Workaround 3 (recommended)

Cause: If the instance already exists, there is no thread-safe problem, you can get the instance directly and reduce the speed problem caused by the lock.

 Public classSingleton {//Lazy Mode//privatize a constructor    PrivateSingleton () {}//instantiating an object    Private Static volatileSingleton instance; //How to get an instance      Public StaticSingleton getinstance () {if(Instance = =NULL) {             synchronized(Singleton.class) {                 if(Instance = =NULL) {instance=NewSingleton (); }             }         }         returninstance; }}

volatile keyword

Simple interest mode (a hungry man mode, lazy mode) thread safety and problem solving