Singleton

Origin: Gof 95
Reason: Ensure that at most one instance of a certain class is created.
Synopsis: Define a class with a private constructor and a public static getInstance method that always return the same instance.
Example: An applet class that ensures that no more than one audioclip is played at a time.
Solution:
Singleton A class of which there is at most one instance.  
See also: Immutable
Note: Java serialization, concurrency, and garbage collection make this a "weak" pattern.