Solved the classcast exception and used instanceof instead. Improved javadocs a bit.

acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/AllModemVisitor.java

@@ -23,8 +23,9 @@
 package com.iluwatar.acyclicvisitor;
 
 /**
- * All ModemVisitor interface extends all visitor interfaces
+ * All ModemVisitor interface extends all visitor interfaces. This interface
+ * provides ease of use when a visitor needs to visit all modem types.
  */
-public interface AllModemVisitor extends ModemVisitor, ZoomVisitor, HayesVisitor{
+public interface AllModemVisitor extends ZoomVisitor, HayesVisitor{
 
 }

acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/ConfigureForUnixVisitor.java

@@ -27,9 +27,10 @@ import org.slf4j.LoggerFactory;
 
 /**
  * ConfigureForUnixVisitor class implements zoom's visit method for Unix 
- * manufacturer
+ * manufacturer, unlike traditional visitor pattern, this class may selectively implement
+ * visit for other modems.
  */
-public class ConfigureForUnixVisitor implements ModemVisitor, ZoomVisitor {
+public class ConfigureForUnixVisitor implements ZoomVisitor {
 
   private static final Logger LOGGER = LoggerFactory.getLogger(ConfigureForUnixVisitor.class);
 

acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/Hayes.java

@@ -37,10 +37,10 @@ public class Hayes extends Modem {
    */
   @Override
   public void accept(ModemVisitor modemVisitor) {
-    try {
-      ((HayesVisitor) modemVisitor).visit(this);
-    } catch (ClassCastException e) {
-      LOGGER.error("Unable to cast to HayesVisitor");
+    if (modemVisitor instanceof HayesVisitor) {
+        ((HayesVisitor) modemVisitor).visit(this);
+    } else {
+        LOGGER.info("Only HayesVisitor is allowed to visit Hayes modem");
     }
 
   }

acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/Zoom.java

@@ -37,10 +37,10 @@ public class Zoom extends Modem {
    */
   @Override
   public void accept(ModemVisitor modemVisitor) {
-    try {
-      ((ZoomVisitor) modemVisitor).visit(this);
-    } catch (ClassCastException e) {
-      LOGGER.error("Unable to cast to ZoomVisitor");
+    if (modemVisitor instanceof  ZoomVisitor) {
+        ((ZoomVisitor) modemVisitor).visit(this);
+    } else {
+      LOGGER.info("Only ZoomVisitor is allowed to visit Zoom modem");
     }
   }