1 Class Overview
1.1 Definitions
1.2 application scenarios
1.3 advantage
1.4 shortcomings
1 Class Overview
1.1 Definitions
Definition: to ensure that only one instance of a class, and provide a global access point
Type: Creating type
1.2 usage scenarios
a ◆ absolutely want to make sure that only one instance of any case
b When an object needs to be created frequently destroyed when, and created or destroyed unable to optimize performance
E.g:
Order of service website counter can use a singleton;
EXAMPLE single mode where the thread pool;
Database connection pool can also use the singleton;
1.3 advantage
In only one instance of a memory, reducing memory overhead
b avoid multiple assignment of resources
c set global access point, and strictly control access (Foreign not be new come out, can not be instantiated)
1.4 shortcomings
No interface is hard to expand