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According to the Java API \[[API 2006|AA. Bibliography#API 06]\] class {{Object}}, method {{hashcode()}} documentation:

Whenever it is invoked on the same object more than once during an execution of a Java application, the hashCode method must consistently return the same integer, provided no information used in equals comparisons on the object is modified. This integer need not remain consistent from one execution of an application to another execution of the same application.

Consequently, the hashcode of an object need not remain consistent across different executions of the application. Similarly, if an object is serialized, its hashcode may not stay consistent with the original value. This introduces several hurdles; for example, upon deserialization of a hashtable, it is impossible to retrieve the contained objects because the corresponding key values may have changed.

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This noncompliant code example uses the {{Key}} class as the key index for the {{Hashtable}}. According to the Java API \[[API 2006|AA. Bibliography#API 06]\] class {{Hashtable}} documentation:

To successfully store and retrieve objects from a hashtable, the objects used as keys must implement the hashCode method and the equals method.

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Serializing objects with implementation defined characteristics can corrupt the state of the object.

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