Error-prone has UnsafeLocaleUsage, detecting the use of the Locale constructors and Locale.toString.
https://errorprone.info/bugpattern/UnsafeLocaleUsage

All good...

But JDK 19 deprecated the constructors and added the static methods Locale.of:

• static Locale Locale.of(String language)
• static Locale Locale.of(String language, String country)
• static Locale Locale.of(String language, String country, String variant)

The methods have the exact same problems as the constructors.
So it would be nice if error-prone would also detect them.