The Sources panel enables you to view the location of the project folder,
manage source and test package folders, as well as set the source level of
the packages which the IDE will use.
You open the Standard J2SE Project Properties dialog box by right-clicking
any
and choosing Properties.
Use the buttons on the right side of the panel to add, remove, and change
the order of classpath elements.
You can have multiple source roots in a standard project, with the following exceptions:
The source root cannot already exist in another IDE project.
The source root cannot already be added to another compilation unit of the same project. For example, a source root that is registered under Test Packages cannot be added to the list of Source Packages.
All of the source roots are packaged into the same JAR file and share the same classpath.
If you have a source root that needs to be used by several projects, you should create a separate project for the source root and set up compilation dependencies between the projects.
You can use the Source Level combo box at the bottom of the Sources page to set the Java platform version that the generated Java code should be compatible with. This setting corresponds to the javac -source option.
Specifying the Source Level does not change the Java platform whose libraries and executables are used to compile and run your project. To set the Java platform that is used for compiling and running your project, click Libraries and set the Java Platform setting accordingly. You cannot set the Source Level of a project to a higher release than the project's Java platform.