A single-instance design pattern for Java Design Patterns (Singleton)

Single Case design mode

The singleton pattern in the daily development uses is also more, as the name implies is a class of objects in the entire system can only have a

Advantages:

1. Singleton mode prevents other objects from instantiating their own copy of a singleton object, ensuring that all objects have access to a unique instance

2, because there is an instance object in the whole system, avoid the frequent creation and destruction of objects, so can save system resources

3. Avoid multiple occupancy of shared resources

4. Create this singleton object yourself, and avoid creating it when you use it.

Disadvantages:

1, the singleton mode does not have the abstraction layer, so the extensibility is poor

2, not applicable to changing objects, if the same type of objects need to be used in different scenarios, the singleton will cause data errors

3, misuse of the singleton mode will bring some negative problems, such as to save system resources to the database connection pool object design as a singleton mode, may result in the sharing connection pool object too many programs and a connection pool overflow, if the instantiated object is not exploited for a long time,

The system is considered garbage and is recycled by GC resulting in loss of object state

　　Lazy mode:

　　　　　　

A Hungry man mode:

Dual Lock mode:

　　　　　　

Summarize:

　　1, lazy mode features: Thread insecure, load classes faster, run time to get objects slower,

2, a Hungry man mode features: Thread safety, load class is slow, run time to get objects faster

3, double lock mode: Thread-safe, load class faster, run-time to get objects at a slower speed

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A single-instance design pattern for Java Design Patterns (Singleton)