This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
s.equals(t) will work since s.equals(t) will compare the values. s == t will compare the objects in the heap. s == u will generate a compilation error. t.equals(u) are not equals since the values are different.