java-design-patterns/singleton/index.md

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layout	title	folder	permalink	categories	tags
pattern	Singleton	singleton	/patterns/singleton/	pattern_cat	pattern_tag

Intent: Ensure a class only has one instance, and provide a global point of access to it.

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

Typical Use Case:

• the logging class
• managing a connection to a database
• file manager

Real world examples:

• java.lang.Runtime#getRuntime()