Although JDeveloper provides loads of libraries out-of-the-box, you often need other libraries in your application. You can easily add these libraries via the project properties. This provides two options: ‘Add Library’ and ‘Add Jar / Directory’. We normally us the Add Library option because it allows to include the JavaDoc and the source code. However make sure that you check the ‘Deployed by Default’ checkbox or else the library will not be included on the classpath and the application will fail with a java.lang.ClassNotFoundException. By the way, we never use Tools -> Manage Libraries because we only use project libraries and never the user or system libraries, because they introduce local dependencies that need to be maintained at every workstation seperately.