A non-serializable ``++Comparator++`` can prevent an otherwise-``++Serializable++`` ordered collection from being serializable. Since the overhead to make a ``++Comparator++`` serializable is usually low, doing so can be considered good defensive programming.


== Noncompliant Code Example

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public class FruitComparator implements Comparator<Fruit> {  // Noncompliant
  int compare(Fruit f1, Fruit f2) {...}
  boolean equals(Object obj) {...}
}
----


== Compliant Solution

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public class FruitComparator implements Comparator<Fruit>, Serializable {
  private static final long serialVersionUID = 1;

  int compare(Fruit f1, Fruit f2) {...}
  boolean equals(Object obj) {...}
}
----


