More Library Puzzlers - Java Puzzlers: Traps, Pitfalls, and Corner Cases - page 255

The main lesson of this puzzle is that a singleton class that implements Serializable must have
a readResolve method that returns its sole instance. A secondary lesson is that it is possible to
implement Serializable unintentionally, by extending a class that implements Serializable or
by implementing an interface that extends Serializable . A lesson for platform designers is that
hidden constructors, such as the one provided by serialization, can harm the reader's intuition about
program behavior.
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