Curiously, the following code compiles cleanly without even a warning — at least on Eclipse 3.0 with the default warning settings (and I couldn't find anything to change there that might be relevant).

// JITest.java:
public class JITest implements JIA, JIB {
    public void a() { }
}

// JIA.java:
public interface JIA {
    public void a();
}

// JIB.java:
public interface JIB {
    public void a();
}
[download]

It's curous to me not because I don't see why this works. It's obvious that it *can* work. But interface clash means a design problem, and I'd expect this to at least warrant a warning.