If you download applications from the Internet, you probably check them with a virus scanner before running them. In general, using applications you get from an unknown source is buyer-beware activity where you know there are risks involved. Most of the time things are fine. I've found only two infected files in all my years surfing BBSs and the Net with my trustworthy Mac-but Mac viruses are much less common than IBM ones. However, if a problem occurs and you don't fix it quickly, you can lose lots of time and money. Because a Java application is no different than any other application, it has no more purely security-related constraints than any other language. Applets, though, are different.
Unlike the people who frequently download applications, most folks who encounter Java applets are real people, not computer experts. When you surf to a given URL, the applets on any of its pages automatically load and execute-unless you've set your browser to keep from running applets. You don't have a chance to run a virus checker or to control the execution environment of the applet. As a result, if you didn't know that Java applets couldn't hurt you, you'd tend to set your browser to avoid running Java. But if most browsers are set not to execute Java applets, a significant part of the appeal of Java goes away. That's why there are extensive security features in Java applets that aren't there for Java applications. The next section walks you through them.
| Note |
When you use Java to write an application, security restrictions are pretty much the same as writing an application in C or SmallTalk. |
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