Applied Design Patterns with Java

Creational :: Singleton (127) {C ch 6}

Example - UML : Spooler

Example - Java :: Patterns\Creational\Singleton

Pattern Concept: to ensure that there is one and only one instance of a class, and to provide global point of access to that instance.

Consequences and issues of the Singleton pattern include:

• subclassing a Singleton can be difficult, since this can only work if the base Singleton class has NOT YET been instantiated;
• it is easy to change a Singleton to allow a small number of instances, whenever that might be needed in an application.

The example Java program is called 'Spooler'.

The UML diagram is above, and the list of Java files is below:

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