.java files in the source directory that are required to build the program. Clicking the Add All in Directory button adds all .java files in the source directory to the file list. Clicking the Add Selected button opens a file chooser from which you can select files to add to the list. You can delete a file by selecting a file name and clicking the Delete button.
javac compiler documentation.
For example:
/tmp/new/java/sun/jws/portfolio
package name = sun.jws.portfolio
root directory = /tmp/new/java
See also: