RFR: 7903964: Fix NPE in JTRegConfiguration.getJDKString

[Jorn Vernee]

On Wed, 5 Mar 2025 16:47:50 GMT, Oleksii Sylichenko <duke at openjdk.org> wrote:

> # This bug appears when
> - The user removes the "Build" target from "Before launch" in the Run Configuration.
> - The user unsets or does not set the Project SDK, or if it has been removed from the file system.
> 
> # Steps to reproduce
> 
> 1. Open a JDK project.
> 2. Open "Project Structure".
> 3. Select an SDK in the Project tab.
> 4. Navigate to "Settings → jtreg".
> 5. Set "JRE = "Default".
> 6. Run a test to automatically create a run configuration, or manually create one with "JRE = Default".
> 7. Open Project Structure again.
> 8. Set SDK = "<No SDK>".
> 9. Edit the previously created Run Configuration and remove the "Build" target from "Before launch".
> 10. Run the previously created Run Configuration.
> 
> ## Expected
> - Error message appeared: "No valid JDK configured for running jtreg tests"
> 
> ## Actual:
> - Nothing happened
> 
> # Implemented Changes
> 
> ## JTRegConfiguration.java
> - Add the `@NotNull` annotation to methods that are missing it but have it in the parent method.
> - Add javadoc to `getJDKString`.
> - Refactor `getJDKString`:
>   - Fix method getJDKString, to prevent NPE when Default SDK for the project was not set
> 
> ## JTRegConfigurationRunnableState.java
> - Change visibility to `public` to eliminate the warning in `JTRegConfiguration#getState`.

These changes look good, but please remove `final` from local variables here as well.

> Nothing happened

When I tested this, it was actually worse: the Run option was disabled entirely, and I had to restart the IDE to bring it back. I have created: [7903964](https://bugs.openjdk.org/browse/CODETOOLS-7903964) Please change the PR title to:


7903964: Fix NPE in JTRegConfiguration.getJDKString

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PR Review: https://git.openjdk.org/jtreg/pull/251#pullrequestreview-2667615169
PR Comment: https://git.openjdk.org/jtreg/pull/251#issuecomment-2706706233