Maybe just a simple

?

TBH I'm not convinced that a lock solves a real problem. In practice, this method cannot be called concurrently, therefore just dissociating reading the field and writing the field back is enough to clarify the intents here:

Map<String, String> headers = this.headers;
this.headers = RESTUtil.merge(headers, authHeaders(config.token()));

@snazy @adutra thanks so much for reviewing

Maybe just a simple?

@snazy I just wanna avoid using synchronized on class. See: https://stackoverflow.com/questions/442564/avoid-synchronizedthis-in-java

TBH I'm not convinced that a lock solves a real problem. In practice, this method cannot be called concurrently, therefore just dissociating reading the field and writing the field back is enough to clarify the intents here:

@adutra "this method cannot be called concurrently" - could you explain why, pls? The RESTUtil.merge(...) function read a volatile variable (headers), so I think synchronized might make sense here.