SerializableStuff.java

// Serializable/externalizable specific

import java.io.*;
class a implements Serializable {
   private void readObject(ObjectInputStream stream)
        throws IOException, ClassNotFoundException {
       if (stream == null) throw new IOException();
       if (stream == null) throw new ClassNotFoundException();
   }

   private void readObjectNoData() throws ObjectStreamException {
       if (this == null) throw new ObjectStreamException(){};
   }


   private Object readResolve()
                    throws ObjectStreamException {
       if (this == null) throw new ObjectStreamException(){};
       return null;
   }

   private Object writeReplace() { return null; }
   private void writeObject(ObjectOutputStream stream) { if (stream==null) return; }

  
}

class b  {
   private void <warning descr="Private method 'readObject(java.io.ObjectInputStream)' is never used">readObject</warning>(ObjectInputStream stream)
        throws IOException, ClassNotFoundException {
       if (stream == null) throw new IOException();
       if (stream == null) throw new ClassNotFoundException();
   }

   private void <warning descr="Private method 'readObjectNoData()' is never used">readObjectNoData</warning>() throws ObjectStreamException {
       if (this == null) throw new ObjectStreamException(){};
   }


   private Object <warning descr="Private method 'readResolve()' is never used">readResolve</warning>()
                    throws ObjectStreamException {
       if (this == null) throw new ObjectStreamException(){};
       return null;
   }

   private Object <warning descr="Private method 'writeReplace()' is never used">writeReplace</warning>() { return null; }
   private void <warning descr="Private method 'writeObject(java.io.ObjectOutputStream)' is never used">writeObject</warning>(ObjectOutputStream stream) { if (stream==null) return; }
}

////////////////////////////

abstract class abstractNoSerializable {
  protected Object readResolve() throws ObjectStreamException {
    return null;
  }
}

class serializableSubclassOfAbstractNoSerializable extends abstractNoSerializable implements Serializable {
  public static void main(String[] args) {
    System.out.println(new serializableSubclassOfAbstractNoSerializable().toString());
  }
  static {
    new a();
    new b();
  }
  static final long serialVersionUID = 20130808044800000L;
}