F.1. Introduction

In Chapter 2, you learned that there are two types of errors—syntax errors and logic errors—and you learned how to eliminate syntax errors from your code. Logic errors do not prevent the application from compiling successfully, but they do cause an application to produce erroneous results when it runs. The JDK includes software called a debugger that allows you to monitor the execution of your applications so you can locate and remove logic errors. The debugger will be one of your most important application development tools. Many IDEs provide their own debuggers similar to the one included in the JDK or provide a graphical user interface to the JDK’s debugger.

This appendix demonstrates key features of the JDK’s debugger using command-line applications that receive no input from the user. The same debugger features discussed here can be used to debug applications that take user input, but debugging such applications requires a slightly more complex setup. To focus on the debugger features, we’ve opted to demonstrate the debugger with simple command-line applications involving no user input. For more information on the Java debugger visit download.oracle.com/javase/6/docs/technotes/tools/windows/jdb.html.