CS 110: Introduction to Computer Science Spring 2008
Debugging Programs
With a little of ‘this’ and object equality
Debugging—finding run-time errors in your program
Compiler/syntax errors—in Java, these are the ones javac tells you about.
maddening for beginning programmers, but really like a helpful grandmother
Run-time errors—when you run a program (java Program) and things don’t work as they
should. These are the ones that can keep you up all night.
How do you debug programs now?
Debugging tools, like the one in Eclipse, can help very, very much!
Debuggers let you run your program to specific points, look at variable values
during execution, and step through the program a statement at a time.
Debugging Terminology
Breakpoints—you can specify that the debugger stop execution at any point in the
program.
Step Over-- When execution is stopped at a statement, you can have the debugger
execute one statement at a time. If it’s a method call, the debugger will execute the entire
method and return execution to the statement after the call.
Step in—Execute one statement, but if it’s a method call stop execution at the top of that
method.
Step return—return execution from the method your in to the caller.
Resume—Tell the debugger to run the program until the next breakpoint.
Instructor Sample—Stepping through a (partial) Mastermind program with Eclipse
