  We study the finite temperature phase transition in 2+1 dimensional compact
QED and its dual theory: Josephson junction. Duality of these theories at zero
temperature was established long time ago by Hosotani. Phase transition in
compact QED is well studied and we employ the `duality' to study the
superconductivity phase transition in a Josephson junction. For a thick
junction we obtain a critical temperature in terms of the geometrical
properties of the junction.
