Select the Configuration.
Select the configuration from the configuration list. Click Configurations tab to get the list of available configuration.
Click Java > JVM Settings tab.
Select Enable Debug checkbox under Debug Java Settings.
Provide JVM options as necessary by clicking the New button.
The default JPDA options are as follows:
If you substitute suspend=y, the JVM starts in suspended mode and stays suspended until a debugger attaches to it. This is helpful if you want to start debugging as soon as the JVM starts. To specify the port to use when attaching the JVM to a debugger, specify address=port_number. Check out the JPDA documentation for a list of debugging options.