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Debugging Programs

If, when you run javac, you get a whole slew of compiler error messages, work on fixing the first couple of errors and then re-compile; the later error messages probably result from javac getting confused after the first error.

If you are on a terminal that doesn't let you scroll back to see the first errors, you can redirect the error messages to a file by using >&. To name the error file errs, type ``javac Prog.java >& errs''; use ``head errs'' to see the first ten lines of that file or ``more errs'' to scroll through the file.

If things are getting really tough, you can use a debugger. All Integrated Development Enviroments (IDEs) have built in debuggers that are very nice. For beginning students, the overhead of figuring out an IDE can be more trouble than it is worth. There is a simple debugger that comes with the standard Java Development Kit (JDK), which we are using. It is called jdb.

Using jdb

Ewerton L. Madruga
Modified by Kevin Klenk