A thread-safe lazy single-case design pattern

First review the simple interest design pattern: The simple interest design pattern is a way for a class to create only one instance of an object for outside use. Simple interest design patterns are divided into lazy and a hungry man: A Hungry man is thread-safe:

1 //a hungry man type simple interest design mode:2  classsingle{3      Private Static FinalSingle =NewSingle ();4      PrivateSingle () {}5       Public StaticSingle getinstance () {6           returns;7      }8}

A hungry man thread-safe, can be used to get the instance of the method to add synchronization or add synchronization code block, but this will lose time efficiency, so that every call will determine whether to have a lock, then you can double the null and synchronous code block method to achieve thread safety, and thus improve the efficiency

1 //a thread-safe lazy single-case design pattern2  Public classSingledemo {3 //lazy, thread-safe, double-judge plus sync thread4      Private StaticSingledemo singledemo=NULL;5      PrivateSingledemo () {}6       Public StaticSingledemo getinstance () {7           if(singledemo==NULL) {8               synchronized(Singledemo.class) {9                    if(singledemo==NULL) {TenSingledemo =NewSingledemo (); One                    } A               } -           } -           returnSingledemo; the      } -}

A thread-safe lazy single-case design pattern