Adding Line Breakpoints 
 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. 
Also, the new breakpoint appears in the Breakpoints View list. 
 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. 
  Debugger
  Java perspectives
  Java editor
  Applying hit counts
  Catching Java exceptions
  Removing breakpoints
  Enabling and disabling breakpoints
  Managing conditional breakpoints
  Setting method breakpoints
  Stepping through the execution of a program 
  Breakpoints view