Core Java™ 2 Volume II - Advanced Features, Seventh Edition

What Are Threads?

Let us start by looking at a program that does not use multiple threads and that, as a consequence, makes it difficult for the user to perform several tasks with that program. After we dissect it, we then show you how easy it is to have this program run separate threads. This program animates a bouncing ball by continually moving the ball, finding out if it bounces against a wall, and then redrawing it. (See Figure 1-1.)

Figure 1-1. Using threads to animate bouncing balls

As soon as you click the Start button, the program launches a ball from the upper-left corner of the screen and the ball begins bouncing. The handler of the ...