With IntelliJ IDEA not just you can create brand new projects, but you can also import existing projects set up and developed using other tools and approaches.
1. Choose the source directory
Click on File → Import Project and indicate the location on disk where the existing project can be found.
You can create a new IntelliJ IDEA project starting from a variety of existing projects. In particular, you can import from an existing Eclipse, Maven or Gradle project. You can also build a new project right from a bunch of source files regardless of specific project files.
2. Choose the target project
Once the source directory is known, IntelliJ IDEA needs to know whether you want to build a new project from scratch using files in the specified location or whether you want IntelliJ IDEA to assume a given project model (i.e., Eclipse, Maven, or Gradle) and proceed in a more automated way.
Let's choose to create a new project from source files.
3. Configure new project
You specify the name and the location of the new project being created from existing source files.
4. Choose files to import
Because in this case there's no known project model to process, the wizard develops through quite a few steps as IntelliJ IDEA find a match about what's available on disk and what a regular Android project requires.
For example, you should indicate whether you want gen and src folders.
Likewise, you are asked to confirm the import of any libraries found in the source project.
Finally, you should indicate the Java SDK and Android platform to be used for the new project.
Finally, at the end of the wizard you have a brand new IntelliJ IDEA project built from existing files and projects.
The new project is now ready for building.