--- a/stress-tester/src/main/java/com/passus/st/client/http/filter/HttpMessageModificationOperations.java	Fri Apr 27 15:33:13 2018 +0200
+++ b/stress-tester/src/main/java/com/passus/st/client/http/filter/HttpMessageModificationOperations.java	Fri Apr 27 16:02:48 2018 +0200
@@ -22,29 +22,25 @@
 
     private static final Logger LOGGER = LogManager.getLogger(HttpMessageModificationFilter.class);
 
-    public abstract static class Operation {
+    static CharSequence extractValue(ValueExtractor extractor, HttpRequest req, HttpResponse resp, HttpFlowContext context) {
+        Object value = HttpFiltersUtils.extractValue(extractor, req, resp, context);
+        if (value instanceof CharSequence) {
+            if (LOGGER.isDebugEnabled()) {
+                LOGGER.debug("extractor={} extracted={}", extractor, value);
+            }
 
-        private Operation() {
+            return (CharSequence) value;
         }
 
+        return null;
+    }
+
+    public static interface Operation {
+
         public abstract void process(HttpRequest req, HttpResponse resp, HttpFlowContext context);
-
-        protected final CharSequence extractValue(ValueExtractor extractor, HttpRequest req, HttpResponse resp, HttpFlowContext context) {
-            Object value = HttpFiltersUtils.extractValue(extractor, req, resp, context);
-            if (value instanceof CharSequence) {
-                if (LOGGER.isDebugEnabled()) {
-                    LOGGER.debug("extractor={} extracted={}", extractor, value);
-                }
-
-                return (CharSequence) value;
-            }
-
-            return null;
-        }
-
     }
 
-    protected static abstract class AbstractRemoveOperation extends Operation {
+    protected static abstract class AbstractRemoveOperation implements Operation {
 
         protected final ValueExtractor nameExtractor;
 
@@ -73,7 +69,7 @@
 
     }
 
-    protected static abstract class AbstractNameValueOperation extends Operation {
+    protected static abstract class AbstractNameValueOperation implements Operation {
 
         protected final ByteString name;
 
@@ -312,7 +308,7 @@
 
     }
 
-    protected static abstract class AddParamOperation extends Operation {
+    protected static abstract class AddParamOperation implements Operation {
 
         protected final ByteString name;
 
@@ -517,7 +513,7 @@
 
     }
 
-    public static class ContentOperation extends Operation {
+    public static class ContentOperation implements Operation {
 
         private final ContentReplacer replacer;
 
@@ -545,7 +541,7 @@
 
     }
 
-    public static class SetMethodOperation extends Operation {
+    public static class SetMethodOperation implements Operation {
 
         private final HttpMethod method;
 
@@ -563,7 +559,7 @@
         }
     }
 
-    public static class SetVersionOperation extends Operation {
+    public static class SetVersionOperation implements Operation {
 
         private final ByteString version;
 
@@ -581,7 +577,7 @@
         }
     }
 
-    public static class SetUriOperation extends Operation {
+    public static class SetUriOperation implements Operation {
 
         private final CharSequence uri;
 
@@ -595,7 +591,7 @@
         }
     }
 
-    public static abstract class SetUrlPartOperation extends Operation {
+    public static abstract class SetUrlPartOperation implements Operation {
 
         @Override
         public void process(HttpRequest req, HttpResponse resp, HttpFlowContext context) {
@@ -658,7 +654,7 @@
         }
     }
 
-    public static class SetUrlPathPos extends Operation {
+    public static class SetUrlPathPos implements Operation {
 
         private final ValueExtractor valueExtractor;
         private final int index;
@@ -704,9 +700,7 @@
         }
     }
 
-    public static class SetUrlPathRegex extends Operation {
-
-        private static final String PATH_ELEMENT_DELIMITER = "/";
+    public static class SetUrlPathRegex implements Operation {
 
         private final ValueExtractor valueExtractor;
         private final RegexValueExtractor regexReplacer;