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            "An inner class is a nested class that is not explicitly or implicitly declared static" \[[JLS 2005|AA. Bibliography#JLS 05]\]. Serialization of inner classes (including local and anonymous classes) is error prone. According to the Serialization Specification \[[Sun 2006|AA. Bibliography#Sun 06]\],:

• Serializing an inner class declared in a non-static context that contains implicit non-transient references to enclosing class instances results in serialization of its associated outer class instance.

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The InnerSer class of this compliant solution does not deliberately fails to implement the Serializable interface.

public class OuterSer implements Serializable {
  private int rank;
  class InnerSer {
    protected String name;
    //...
  }
}

Compliant Solution

It is allowable to declare the The inner class may be declared static to prevent its serialization. It is also permissible for a A static inner class to may also implement Serializable.

public class OuterSer implements Serializable {
  private int rank;
  static class InnerSer implements Serializable {
    protected String name;
    //...
  }
}

...