@Override
    public Future<?> shutdownGracefully() {
        return group.shutdownGracefully();
    }
@Test
    public void testInvalidGroup() {
        final EventExecutorGroup group = new DefaultEventExecutorGroup(1);
        try {
            assertThrows(IllegalArgumentException.class, new Executable() {
                @Override
                public void execute() {
                    new NonStickyEventExecutorGroup(group);
                }
            });
        } finally {
            group.shutdownGracefully();
        }
    }