How do you input command line arguments in IntelliJ IDEA?

Windows, Linux, some Macs:

ALT+SHIFT+F10, Right, E, Enter, Tab, enter your command line parameters, Enter. ;-)

Mac with "OS X 10.5" key schema:

CTRL+ALT+R, Right, E, Enter, Tab, enter your command line parameters, Enter.

There's an "edit configurations" item on the Run menu, and on the pull-down to the left of the two green "run" and "debug" arrows on the toolbar. In that panel, you create a configuration with the "+" button in the top left, and then you can choose the Class containing main(), add VM parameters and command-line args, specify the working directory and any environment variables.

There are other options there as well: code coverage, logging, build, JRE, etc.

If you are using intellij go to Run > Edit Configurations menu setting. A dialog box will appear. Now you can add arguments to the Program arguments input field.