BAEL-39 - adding SLF4J examples

log4j/src/main/java/com/baeldung/slf4j/Slf4jExample.java

@@ -0,0 +1,20 @@
+package com.baeldung.slf4j;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * To switch between logging frameworks you need only to uncomment needed framework dependencies in pom.xml
+ */
+public class SLF4JExample {
+    private static Logger logger = LoggerFactory.getLogger(SLF4JExample.class);
+
+    public static void main(String[] args) {
+        logger.debug("Debug log message");
+        logger.info("Info log message");
+        logger.error("Error log message");
+
+        String variable = "Hello John";
+        logger.debug("Printing variable value {} ", variable);
+    }
+}