java.lang.System.Logger.log is specified to accept the message format of MessageFormat. However, the current SLF4JPlatformLogger implementation uses String.format instead of MessageFormat. As a result, the current implementation cannot format the message correctly.

Expected and actual behavior

LoggerFinder finder = System.LoggerFinder.getLoggerFinder();
Logger systemLogger = finder.getLogger("smoke", null);
systemLogger.log(Level.INFO, "hello {0}", "world");

 
Expected output:

INFO smoke - hello world

Actual output:

INFO smoke - hello {0}