Let's say I have the following Java interface that I may not modify:

public interface MyInterface {
  public void doSomething();
}

And now the class implementing it is like this:

class MyImplementation implements MyInterface {
  public void doSomething() {
    try {
      // read file
    } catch (IOException e) {
      // what to do?
    }
  }
}

I can't recover from not reading the file.

A subclass of RuntimeException can clearly help me, but I'm not sure if it's the right thing to do: the problem is that that exception would then not be documented in the class and a user of the class would possibly get that exception an know nothing about solving this.

What can I do?