Java Record -19-Singleton mode

Design mode (pattern)

Singleton mode (Singleton), and list state mode.

There is only one instance of a class that is used in the process.

Note the point:

1. The instance variable is static;
   

2. The construction method is private;

3. The method that provides the instance is static.

Because the construction method is private, the construction method cannot be used for instance construction outside.

To be used, you must provide a static method of returning the instance, which can be invoked using the class name.

Java Record -19-Singleton mode