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<ac:structured-macro ac:name="anchor" ac:schema-version="1" ac:macro-id="92763b0258a0e6cb-aea14534-494e4f54-b01197e4-83b49b65d126a8defe60c979"><ac:parameter ac:name="">CON03-EX1</ac:parameter></ac:structured-macro> *CON03-EX1:* It is permissible to start a background thread during class initialization provided the thread does not access any fields. For example, the {{ObjectPreserver}} class (based on \[[Patterns 02|AA. Java References#Patterns 02]\]) shown below provides a mechanism for storing object references, which prevents an object from being garbage-collected, even if the object is not dereferenced in the future. |
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This is a singleton class. (See CON23MSC16-J. Address the shortcomings of the Singleton design pattern for more information on how to defensively code singleton classes.) The initialization involves creating a background thread using the current instance of the class. The thread waits indefinitely by invoking Object.wait(). Consequently, this object exists for the remainder of the Java Virtual Machine's (JVM's) lifetime. Because the object is managed by a daemon thread, the thread does not hinder a normal shutdown of the JVM.
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