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Debugging in BlueJ

Debugging in BlueJ. Davin McCall. Overview. What is debugging? Object inspector Method invocation “Traditional” BlueJ debugger window Demo Questions. Debugging…. Locate the source of a bug Run through the part of the program where we think the bug is occurring, watch program behaviour

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Debugging in BlueJ

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  1. Debugging in BlueJ Davin McCall First BlueJ Day, Houston, Texas, 1st March 2006

  2. Overview • What is debugging? • Object inspector • Method invocation • “Traditional” BlueJ debugger window • Demo • Questions First BlueJ Day, Houston, Texas, 1st March 2006

  3. Debugging… • Locate the source of a bug • Run through the part of the program where we think the bug is occurring, watch program behaviour • In BlueJ this is normal operation!! (to some extent) - inspectors, method invocation • BlueJ also has a (simple) more traditional debugger First BlueJ Day, Houston, Texas, 1st March 2006

  4. Debugging (cont’d) • Set “breakpoints” which will halt the program execution when reached • Once execution is halted, can continue execution line by line (“stepping”), either following or stepping over function calls • Inspect values of variables in currently executing methods (the stack). Inspected objects shown in familiar inspector windows First BlueJ Day, Houston, Texas, 1st March 2006

  5. Stepping • Stepping through code … • Might let us see what is going wrong • Also serves as a good way to demonstrate control structure behavior, program flow, etc First BlueJ Day, Houston, Texas, 1st March 2006

  6. BlueJ as a debugger • Even without the debugger window, BlueJ offers unique features which can be used for debugging and testing • Construct objects on the fly • Call arbitrary methods interactively • Inspect objects and classes to see field values First BlueJ Day, Houston, Texas, 1st March 2006

  7. Conclusion • BlueJ provides basic debugging functionality • Some of BlueJ’s core features (interactive invocation and inspection) are also useful for debugging • Debugging techniques can serve another purpose: demonstrating code behaviour First BlueJ Day, Houston, Texas, 1st March 2006

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