Sometimes while debugging your program, you want to simply log the value of certain expression at a certain point in your program's logic. You do not want to neccessarily look at it every time a breakpoint is hit. In fact you may not even want the program to stop at the breakpoint at all. This is possible in Netbeans Debugger by customizing the breakpoint the following way:

  • set Print Text: to what ever you want to print. The text is printed in the Debug Console tab of the Output window.
  • set Suspend: to No Thread (continue). This makes the program to continue running after performing the Print Text: action.

For example given the following program:

with a breakpoint at line 7 customized like this:

gives the following output:

IMPORTANT: Notice the expressions like {=i} and {=sum} in the Print Text: field. The variables i and sum are from the user program. Using the {=expression} syntax you can print the value of any expressions that are valid in the context of the breakpoint. There is bug in Netbeans online help which shows a wrong syntax for embedded expressions i.e. {$expression} (incorrect!) instead of {=expression} (correct!). Hopefully this will get corrected soon (I have already filed a bug).

Note that there are several other built-in variables - such as {className}, {methodName} that can be used in Print Text: field. Not all the built-ins are available with all types of breakoints. See the online help for details.

Source: sandip chitale's blog