Eclipse can't find / load main class

Question

My Eclipse (Indigo) was running just fine. I created a simple class Hello. It is placed in package cont in the folder ch13. However

Answer 1

Another tip: I initialized static fields in a wrong order - surprisingly it didn't bring up a Problem (NullPointerException?), instead Eclipse complained with exactly the message OP posted. Correcting the static initialization order made the class run-able. Example:

private static ScriptEngineManager factory = null;
private static ScriptEngine engine = null;
static {
    engine = factory.getEngineByName("JavaScript");
    // factory is supposed to initialize FIRST
    factory = new ScriptEngineManager();
}