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""Since there is only one Singleton instance, any instance fields of a Singleton will occur only once per class, just like {{static}} fields. Singletons often control access to resources such as database connections or sockets."" \[[Fox 01|AA. Java References#Fox 01]\]. Other applications of singletons involve maintaining performance statistics, system monitoring and logging, implementing printer spoolers or as simple as ensuring that only one audio file plays at a time. 

Bloch \[[Bloch 08|AA. Java References#Bloch 08]\] suggests the use of an {{enum}} type as a replacement for traditional implementations (shown below). Functionally, this approach is equivalent to commonplace implementations. It ensures that only one instance of the object exists at any instant and also provides the serialization property as {{java.lang.Enum&lt;E&gt;Enum<E>}} extends {{Serializable}}.

\[[JLS 05|AA. Java References#JLS 05]\] [Chapter 17, Threads and Locks|http://java.sun.com/docs/books/jls/third_edition/html/memory.html]
\[[Fox 01|AA. Java References#Fox 01]\] [When is a Singleton not a Singleton?|http://java.sun.com/developer/technicalArticles/Programming/singletons/] 
\[[Daconta 03|AA. Java References#Daconta 03]\] Item 15: Avoiding Singleton Pitfalls;
\[[Darwin 04|AA. Java References#Darwin 04]\] 9.10 Enforcing the Singleton Pattern
\[[Gamma 95|AA. Java References#Gamma 95]\] Singleton
\[[Patterns 02|AA. Java References#Patterns 02]\] Chapter 5, Creational Patterns, Singleton
\[[Bloch 08|AA. Java References#Bloch 08]\] Item 3: ""Enforce the singleton property with a private constructor or an enum type""
\[[MITRE 09|AA. Java References#MITRE 09]\] [CWE ID 543|http://cwe.mitre.org/data/definitions/543.html] ""Use of Singleton Pattern in a Non-thread-safe Manner""