A library is an archive of compiled code (such as JAR files) that your modules depend on. The IntelliJ Platform supports three types of libraries:

• Module Library: the library classes are visible only in this module and the library information is recorded in the module *.iml file.
• Project Library: the library classes are visible within the project and the library information is recorded in the project *.ipr file or in .idea/libraries.
• Global Library: the library information is recorded in the applicationLibraries.xml file into the <User Home>/.IntelliJIdea/config/options directory. Global libraries are similar to project libraries, but are visible for the different projects.

For more information about libraries, refer to Library.

Accessing Libraries and Jars

Package libraries provides functionality for working with project libraries and jars. Libraries and jars can be retrieved like the following snippet shows

ProjectFileIndex fileIndex = ProjectRootManager.getInstance(project).getFileIndex();
OrderEntry orderEntry : fileIndex.getOrderEntriesForFile(virtualFile));

Checking Belonging to a Library

The ProjectFileIndex interface implements a number of methods you can use to check whether the specified file belongs to the project library classes or library sources. You can use the following methods:

• To check if a specified virtual file is a compiled class file use

  ProjectFileIndex.isLibraryClassFile(virtualFile)
  

• To check if a specified virtual file or directory belongs to library classes use

  ProjectFileIndex.isInLibraryClasses(virtualFileorDirectory)
  

• To check if the specified virtual file or directory belongs to library sources use

  ProjectFileIndex.isInLibrarySource(virtualFileorDirectory)
  

See the following code sample to see how the method mentioned above can be applied.

Note: By default, the project modules use the project SDK. Optionally, you can configure individual SDK for each module.

More details on libraries can be found in this code sample