In General, the cause of the title problem is the incompatibility between the version of JDK used in the project and properties responsible for compatibility of the source and target code.
Library dependency management is one of the most missing tools in Oracle JDeveloper 11g. It is true that Maven support has been added in JDeveloper 12c. Nevertheless, in the older projects you may want to use Gralde integration described in this article. This approach also works with JDeveloper 12c.