Applied Design Patterns with Java

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

Applicability

Use the Singleton pattern when:

• there must be exactly one instance of a class, and it must be accessible to clients from a well-known access point;
• when the sole instance should be extensible by subclassing, and clients should be able to use an extended instance without modifying their code.

Structure

Participants

Singleton -

• defines an Instance operation that lets clients access its unique instance. Instance is a class operation, i.e.: a static (class method) in Java and a static member function in C++.
• may be responsible for creating its own unique instance.

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