Hiding Unsafe Methods Through Polymorphism

Recently I have been thinking of using additional interfaces in one of my libraries to hide certain "unsafe" methods of my classes from the user. I would like to get the opinion of other, more advanced java programmers on this issue.
What I do is something like the following (heavily simplified):

public interface ReadOnly {
public int getValue();
}
 public interface ReadWrite extends ReadOnly {
public void setValue(int value);

[Code] ....

The user would have access to the ExternalInterface. The ExternalInterface is controlling the values of the InternalComponent. The user can get the InternalComponent, but typecasted to a ReadOnly which does not expose the setters.

Now the thing is the user can still access the setValue method by typecasting the ReadOnly to an InternalComponent or to a ReadWrite, and that is not bad. If the user knows exactly what he/she is doing this will give him/her more flexibility and more power. But this way it *should* become obvious that this is not the intended use and perhaps the extra work of typecasting will discourage the user from doing this.