<image> As shown in the figure, the graph of the function $$y_{1}=-x+4$$ intersects with the graph of the function $$y_{2}= \dfrac {k_{2}}{x}(x > 0)$$ at points $$A(a,1)$$ and $$B(1,b)$$.
$$(1)$$ Find the expression of the function $$y_{2}$$;
$$(2)$$ Observe the graph and compare the values of $$y_{1}$$ and $$y_{2}$$ when $$x > 0$$.