Introduction to Programming Using Java is a free on-line textbook. Read the chapter on Applets and GUIs, http://www.faqs.org/docs/javap/c6/index.html You might find it helpful to take the quiz at the end of the chapter. (There is a link to the answers so you can grade yourself.) The programming exercises are worth trying. They also have sample solutions.

Other tutorials on Applets and GUIs: http://www.realapplets.com/tutorial/ and http://jtf.acm.org/tutorial/GraphicalUserInterfaces.html

Assignment:
Creat an applet to calculate compound interest. Provide textboxes for the present value (PV), interest rate (i), and number of periods (n). The equation is FV = PV(1+i)^n where Future Value (FV) is the amount the user will have at the end of the timespan. Provide a button to (re)caluclate the FV.
Note: The pow method of the Math class performs exponentiation.