Java applets are java programs that run on your PC inside the browser environment. In order to run them you must have the Java plug in for your browser, just like you need the Flash plug in to see Flash movies. Applets cannot write to your hard drive or do much of anything for security reasons. They are used on some sites to provide powerful stock market graphing capabilities much faster than regenerating pages and downloading them from a server can do. Applets have also been useful in games and in on line training such as the excellent Java Ranch 'roundup' game . It is a mock exam for the SCJP test. Java applets can take full advantage of powerful Java2D image processing capabilities. Applets can communicate via http only with the server that spawned them.

Applet1 will appear below in a Java enabled browser. This very simple applet just counts in a thread and displays the number.