Question

I want a method that can throw any Throwable including sub classes of Exception. Ive got something that takes an exception, stashes it in a thread local, then invokes a class.newInstance. That class ctor declares that it throws Exception then takes the threadlocal and throws it. Problem is it does not work for the two declared Exceptions thrown by Class.newInstance() namely IllegalAccessException and InstantiationException.

Im guessing any other method using some sun.* class is just a hack and not really reliable.

Wrapping is not an option because that means catchers are catching a diff type and that’s just too simple and boring…

    static public void impossibleThrow(final Throwable throwable) {
    Null.not(throwable, "throwable");
    if (throwable instanceof RuntimeException) {
        throw (RuntimeException) throwable;
    }
    if (throwable instanceof Error) {
        throw (Error) throwable;
    }
    try {
        THROW.set((Exception) throwable);
        THROWER.newInstance();
    } catch (final InstantiationException screwed) {
        throw new Error(screwed);
    } catch (final IllegalAccessException screwed) {
        throw new Error(screwed);
    } finally {
        THROW.remove();
    }
}

private final static Class<Impossible> THROWER = Impossible.class;
private final static ThreadLocal<Exception> THROW = new ThreadLocal<Exception>();

static private class Impossible {

    @SuppressWarnings("unused")
    public Impossible() throws Exception {
        throw THROW.get();
    }
}

Answer 1

From Java Puzzlers (puzzle 43):

public static void impossibleThrow(Throwable t)
{
    Thread.currentThread().stop(t); // Deprecated method.
}

The book shows other methods of achieving the same problem, one is a simplified version of yours, the other exploits generic type erasure to throw any Throwable where an Error is expected.