To debug a Java class using the Eclipse IDE, you must create a breakpoint. It can be made by simply double-clicking near the line number (a blue round will be displayed). Then, when you click on the debug button to run the debugging process, the execution of the class will stop right on the line marked with the breakpoint, and you may type the following keys on the keyboard:
The following screenshot shows the Eclipse debug screen. There is an important section in this screen on the right-top corner named Variables that shows the variables and its respective current values.