Background

It is necessary to debug a patched version of JDK, and at the same time have a default one w/o modifications

Question

How to prioritize a list of "sourcepath" under File | Project Structure | SDKs | Sourcepath?

Answer

If you have two JDK versions—one with a patch and another with the default sources—you can create separate copies of each JDK on your machine and add them individually via File | Project Structure | SDKs | Add new SDK, assigning the appropriate source set to each. Then, switch between them as needed via File | Project Structure | Project—use the patched version when debugging, or switch back to the default as necessary.

IntelliJ IDEA should pick a JDK defined under File | Project Structure | Project on a runtime