Slf4J is not an alternative for Log4j, but rather provides a Façade for logging, so one can you can plug in your own logging framework. It's mainly useful for libraries.
from slf4j.org:
The Simple Logging Facade for Java or
(SLF4J) serves as a simple facade or
abstraction for various logging
frameworks, e.g. java.util.logging,
log4j and logback, allowing the end
user to plug in the desired logging
framework at deployment time.
To answer your question: Slf4j is being adopted by frameworks now, but in your projects, you can keep on using Log4J (or any other)
