Refusal to use marker interface as parameter?

Question

Heya all,
I've seen a lot of professional (ie Apache, Sun, etc) Java code that has code similar to this:
public void serialise(Object o)
   if (o instanceof Serializable)
      throw new IllegalArgumentException("Object is not serializable");
   ... code here...
}Whereas surely it could be re-written as:
public void serialise(Serializable o)
   ... code here...
}Thus giving us compile-time type safety. I seem to get the impression that 'Serializable' and 'Cloneable' and other such 'marker' interfaces shouldn't be used as parameters in this way because they are not 'real' interfaces as such. I usually prefer the second form; but I have seen both forms fairly commonly.
Any comments/suggestions on when it's better to use different ways?

Answer 1

Then allow me to be more specific, without retracting my original point. The following methods within java.io.ObjectInputStream and java.io.ObjectOutputStream which current exist as:
public Object readObject() throws IOException {}
public void writeObject(Object object) throws IOException {}Could easily be re-written (and be more specific and type-safe) via the following declarations:
public Serializable readObject() throws IOException{}
public void writeObject(final Serializable object) throws IOException {}I would further propose renaming then SerializableInputStream and SerializableOutputStream, as they do not truly take all instances of java.lang.Object.
- Saish