Line breakpoints are set on an executable line of a program.
In the editor area, open the file where you want to add the breakpoint.
Directly to the left of the line where you want to add the breakpoint,
open the marker bar (vertical ruler) pop-up menu and select Toggle
Breakpoint. You can also double-click on the marker bar
next to the source code line. A new breakpoint marker appears on the
marker bar, directly to the left of the line where you added the breakpoint.
While the breakpoint is enabled, thread execution suspends before that line of code is executed. The debugger selects
the thread that has suspended and displays the thread's stack
frames. The line where the breakpoint was set is highlighted in the editor in the Debug Perspective.