Launching a Java program in debug mode

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,

In the Package Explorer, select the Java compilation unit or class file with the main method you want to launch.
Press the Debug [ ] 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.
Your program is now launched and the launched process appears in the Debug view.

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.)