Serializing a non-``++static++`` inner class will result in an attempt at serializing the outer class as well. If the outer class is not serializable, then serialization will fail, resulting in a runtime error. 


Making the inner class ``++static++`` (i.e. "nested") avoids this problem, therefore inner classes should be ``++static++`` if possible. However, you should be aware that there are semantic differences between an inner class and a nested one: 

* an inner class can only be instantiated within the context of an instance of the outer class. 
* a nested (``++static++``) class can be instantiated independently of the outer class.


== Noncompliant Code Example

----
public class Pomegranate {
  // ...

  public class Seed implements Serializable {  // Noncompliant; serialization will fail
    // ...
  }
} 
----


== Compliant Solution

----
public class Pomegranate {
  // ...

  public static class Seed implements Serializable {
    // ...
  }
} 
----


== See

* https://wiki.sei.cmu.edu/confluence/x/ZTdGBQ[CERT SER05-J.] - Do not serialize instances of inner classes

