One calls in with a problem. Of course, the customer doesn't remember, not exactly enough. That log file contains a record of what she did. Usability analysts Appropriate trace messages can be used to record which features are most used, and how they're used. Skilled testers watch for oddities and escalate them into important bugs.
Information printed in trace statements can help such testers.
Trace statements can also help a tester know if a test is really doing what was intended. If your company operates a server, Trace.java can be used to add important information to the server log. Features Trace messages identify the method, filename, and line number from which they came. On error, the buffer can be dumped into the log. Trace messages have seven predefined levels.