SLF4J implements a single Logger for J.U.L. that redirects log statements to SLF4J. This has significant performance implications as every log statement is processedby J.U.L. so it can then be forwarded to SLF4J. To avoid this, SLF4J should implement java.util.logging.LogManager and register this with J.U.L. to handle log statements. This is how application servers are able to implement their own logging system using the J.U.L. API without performance penalty.

So, for example, there would be an org.slf4j.jul.LogManager implementation of java.util.logging.LogManager. This would then be registered with J.U.L. using the system property "java.util.logging.manager".