Project Root. The project root specifies the directory that corresponds to the default package of the project. All project files should be located in this directory or one of its subdirectories.
Build Directory. The project facility allows the user to set a build directory where class files will be compiled. This gives the user the ability to separate source and class files. This setting is required for the "Clean Build Directory" and "Create Jar from Project" features to work correctly.
To clean the build directory, open the Project Menu and click "Clean Build Directory." This will remove all .class files and empty directories in the build directory.
Working Directory. The working directory corresponds to "current" directory of the project, i.e. new File(".") or System.getProperty("user.dir").
Main Document. The project facility allows the user to specify a "Main Document" file for your project. When the "Run Project" button is pressed or the "Run Main Document of Project" is then selected in the Project menu, the main method of the "Main Document" file specified will be executed. If no "Main Document" is specified, the "Run Main Document of Project" item will not be available, and the "Run Project" button is replaced by the "Run" button that runs the main method of the current document.
Extra Classpath. In the "Extra Classpath" area, you may add additional directories or jar files to the project's classpath.