Launching a program in debug mode allows you to suspend and resume the program, inspect variables, and evaluate expressions using the debugger.
To launch a Java program in debug mode,
] button in the workbench toolbar
or select Run > Debug from the workbench menu bar.
Alternatively you can select Run > Debug As > Java
Application from the workbench menu bar, or select
Debug As > Java Application in the Package
Explorer pop-up menu or in the drop-down menu on the
Debug tool bar button.
If you want your program to stop in the main method so that you can step through its complete execution, create a Java Application launch configuration and check the Stop in main checkbox on the Main tab.
You can also debug a Java program by selecting a project instead of the compilation unit or class file. You will be prompted to select a class from those classes that define a main method. (If only one class with a main method is found in the project, that class is launched as if you selected it.)