[LOGMGR-327] Add an isEmpty() method for MDC.

src/main/java/org/jboss/logmanager/MDC.java

@@ -139,6 +139,15 @@ public static Map<String, Object> copyObject() {
         return mdcProvider.copyObject();
     }
 
+    /**
+     * Checks of the MDC map is empty.
+     *
+     * @return {@code true} if the MDC map is empty, otherwise {@code false}
+     */
+    public static boolean isEmpty() {
+        return mdcProvider.isEmpty();
+    }
+
     /**
      * Clear the current MDC map.
      */

src/main/java/org/jboss/logmanager/MDCProvider.java

@@ -68,6 +68,13 @@ public interface MDCProvider {
      */
     Map<String, Object> copyObject();
 
+    /**
+     * Returns {@code true} if the backing MDC map is empty, otherwise {@code false}.
+     *
+     * @return {@code true} if the MDC map is empty
+     */
+    boolean isEmpty();
+
     /**
      * Clear the current MDC map.
      */

src/main/java/org/jboss/logmanager/ThreadLocalMDC.java

@@ -58,6 +58,11 @@ public Map<String, Object> copyObject() {
         return mdc.get().clone();
     }
 
+    @Override
+    public boolean isEmpty() {
+        return mdc.get().isEmpty();
+    }
+
     @Override
     public void clear() {
         mdc.get().clear();