Singleton Pattern: Use All Static Methods or Private Constructor?

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#7700

From: Jack Frosch
Date: Mon, 28 May 2001 16:56

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IN their book "Design Patterns" the GoF defines the Singleton pattern's
intent thus: "To ensure a class has only one instance, and provide a global
point of access to it."

For Java implementations, I've seen two implementation variations to achieve
this:

1) Some people code all static methods and data in a class, thus ensuring
only one "instance" of the class exists in the VM.

2) Others use an implementation where the class is defines as normal, but
with a private constructor.  A single public, static method is provided to
the single instance of the class that's stored as a private instance
variable.

Approach #2 clearly meets the pattern description of the GoF, but I'm
wondering if there are any uniquely-Java reasons why approach #1 might be
preferable?

Thanks.

Jack

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Subject: Singleton Pattern: Use All Static Methods or Private Constructor?
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