22. The API (Application Programming Interface) documentation lists the classes
and methods of the Java library.
23. An object reference describes the location of an object.
24. Multiple object variables can contain references to the same object.
25. Number variables store numbers. Object variables store references.
26. To show a frame, construct a JFrame object, set its size, and make it visible.
27. In order to display a drawing in a frame, define a class that extends the
28. Place drawing instructions inside the paintComponent method. That method
is called whenever the component needs to be repainted.
29. The Graphics class lets you manipulate the graphics state (such as the current
30. The Graphics2D class has methods to draw shape objects.
31. Use a cast to recover the Graphics2D object from the Graphics parameter
of the paintComponent method.
32. Applets are programs that run inside a web browser.
33. To run an applet, you need an HTML file with the applet tag.
34. You view applets with the applet viewer or a Java-enabled browser.
35. Ellipse2D.Double and Line2D.Double are classes that describe
36. The drawString method draws a string, starting at its basepoint.
37. When you set a new color in the graphics context, it is used for subsequent