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java-design-patterns/singleton/README.md
Ilkka Seppälä e57a0948ef Merge pull request #490 from iluwatar/DocumentUsages 
#211 Document GoF usages from Java API
2016-09-03 14:14:13 +03:00

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layout title folder permalink pumlid categories tags
pattern Singleton singleton /patterns/singleton/ HSV14SCm20J0Lk82BFxf1ikCh0n26ZZizfDVVhjRjwfvIhg-Bc35cyZvAQtZoYD3l4w364gTWxhcms2d3z-ydnAzsRuO4BUWmV43HRUcWcaagF-Lz55M3lq2 Creational
Java
Gang Of Four
Difficulty-Beginner

Intent

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

alt text

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

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