diff --git a/jetty-server/src/main/java/org/eclipse/jetty/server/handler/ContextHandlerCollection.java b/jetty-server/src/main/java/org/eclipse/jetty/server/handler/ContextHandlerCollection.java
index e2b127272eb..cbdb52528d4 100644
--- a/jetty-server/src/main/java/org/eclipse/jetty/server/handler/ContextHandlerCollection.java
+++ b/jetty-server/src/main/java/org/eclipse/jetty/server/handler/ContextHandlerCollection.java
@@ -43,8 +43,7 @@ import org.eclipse.jetty.util.log.Logger;
 import org.eclipse.jetty.util.thread.SerializedExecutor;
 
 /* ------------------------------------------------------------ */
-/** ContextHandlerCollection.
- *
+/**
  * This {@link org.eclipse.jetty.server.handler.HandlerCollection} is creates a
  * Map of contexts to it's contained handlers based
  * on the context path and virtual hosts of any contained {@link org.eclipse.jetty.server.handler.ContextHandler}s.
@@ -87,10 +86,8 @@ public class ContextHandlerCollection extends HandlerCollection
     protected Handlers newHandlers(Handler[] handlers)
     {
         if (handlers==null || handlers.length==0)
-        {
             return null;
-        }
-        
+
         // Create map of contextPath to handler Branch
         // A branch is a Handler that could contain 0 or more ContextHandlers
         Map<String,Branch[]> path2Branches = new HashMap<>();
@@ -133,7 +130,7 @@ public class ContextHandlerCollection extends HandlerCollection
                     continue loop;
                 }
             }
-            break loop;
+            break;
         }
         
         if (LOG.isDebugEnabled())
@@ -156,9 +153,6 @@ public class ContextHandlerCollection extends HandlerCollection
     }
 
     /* ------------------------------------------------------------ */
-    /*
-     * @see org.eclipse.jetty.server.server.Handler#handle(java.lang.String, javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse, int)
-     */
     @Override
     public void handle(String target, Request baseRequest, HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException
     {
@@ -167,9 +161,6 @@ public class ContextHandlerCollection extends HandlerCollection
             return;
 
         Mapping mapping = (Mapping)handlers;
-        if (mapping==null)
-            return;
-
         HttpChannelState async = baseRequest.getHttpChannelState();
         if (async.isAsync())
         {
@@ -230,7 +221,9 @@ public class ContextHandlerCollection extends HandlerCollection
     }
 
     /* ------------------------------------------------------------ */
-    /** Add a context handler.
+    /**
+     * Adds a context handler.
+     *
      * @param contextPath  The context path to add
      * @param resourceBase the base (root) Resource
      * @return the ContextHandler just added
@@ -273,7 +266,6 @@ public class ContextHandlerCollection extends HandlerCollection
     }
 
     /* ------------------------------------------------------------ */
-    public void undeployHandler(Handler handler)
     /**
      * Thread safe undeploy of a Handler.
      * <p>
@@ -285,6 +277,7 @@ public class ContextHandlerCollection extends HandlerCollection
      * </p>
      * @param handler The handler to undeploy
      */
+    public void undeployHandler(Handler handler)
     {
         _serializedExecutor.execute(()-> removeHandler(handler));
     }
@@ -298,7 +291,6 @@ public class ContextHandlerCollection extends HandlerCollection
         return _contextClass;
     }
 
-
     /* ------------------------------------------------------------ */
     /**
      * @param contextClass The class to use to add new Contexts
@@ -338,7 +330,7 @@ public class ContextHandlerCollection extends HandlerCollection
         
         Set<String> getContextPaths()
         {
-            Set<String> set = new HashSet<String>();
+            Set<String> set = new HashSet<>();
             for (ContextHandler context:_contexts)
                 set.add(context.getContextPath());
             return set;
@@ -380,7 +372,7 @@ public class ContextHandlerCollection extends HandlerCollection
         Mapping(Handler[] handlers, int capacity)
         {
             super(handlers);
-            _pathBranches = new ArrayTernaryTrie(false, capacity);
+            _pathBranches = new ArrayTernaryTrie<>(false, capacity);
         }
     }
 }
diff --git a/jetty-server/src/main/java/org/eclipse/jetty/server/handler/HandlerCollection.java b/jetty-server/src/main/java/org/eclipse/jetty/server/handler/HandlerCollection.java
index 1a8d7601aee..c90be145f21 100644
--- a/jetty-server/src/main/java/org/eclipse/jetty/server/handler/HandlerCollection.java
+++ b/jetty-server/src/main/java/org/eclipse/jetty/server/handler/HandlerCollection.java
@@ -72,7 +72,7 @@ public class HandlerCollection extends AbstractHandlerContainer
     
     /* ------------------------------------------------------------ */
     /**
-     * @return Returns the handlers.
+     * @return the array of handlers.
      */
     @Override
     @ManagedAttribute(value="Wrapped handlers", readonly=true)
@@ -84,7 +84,7 @@ public class HandlerCollection extends AbstractHandlerContainer
 
     /* ------------------------------------------------------------ */
     /**
-     * @param handlers The handlers to set.
+     * @param handlers the array of handlers to set.
      */
     public void setHandlers(Handler[] handlers)
     {
@@ -93,9 +93,9 @@ public class HandlerCollection extends AbstractHandlerContainer
 
         while(true)
         {
-            if(updateHandlers(_handlers.get(),newHandlers(handlers)))
+            if (updateHandlers(_handlers.get(), newHandlers(handlers)))
                 break;
-        };
+        }
     }
 
     /* ------------------------------------------------------------ */
@@ -123,10 +123,11 @@ public class HandlerCollection extends AbstractHandlerContainer
                     handler.setServer(getServer());
         }
 
-
-        if (_handlers.compareAndSet(old,handlers))
+        if (_handlers.compareAndSet(old, handlers))
         {
-            updateBeans(old==null?null:old._handlers,handlers==null?null:handlers._handlers);
+            Handler[] oldBeans = old == null ? null : old._handlers;
+            Handler[] newBeans = handlers == null ? null : handlers._handlers;
+            updateBeans(oldBeans, newBeans);
             return true;
         }
         return false;
@@ -143,28 +144,21 @@ public class HandlerCollection extends AbstractHandlerContainer
             if (handlers==null)
                 return;
 
-            Handler[] h = handlers._handlers;
-
             MultiException mex=null;
-
-            for (int i=0;i<h.length;i++)
+            for (Handler handler : handlers._handlers)
             {
                 try
                 {
-                    h[i].handle(target,baseRequest, request, response);
+                    handler.handle(target, baseRequest, request, response);
                 }
-                catch(IOException e)
+                catch (IOException | RuntimeException e)
                 {
                     throw e;
                 }
-                catch(RuntimeException e)
+                catch (Exception e)
                 {
-                    throw e;
-                }
-                catch(Exception e)
-                {
-                    if (mex==null)
-                        mex=new MultiException();
+                    if (mex == null)
+                        mex = new MultiException();
                     mex.add(e);
                 }
             }
@@ -179,9 +173,9 @@ public class HandlerCollection extends AbstractHandlerContainer
     }
 
     /* ------------------------------------------------------------ */
-    /* Add a handler.
+    /**
+     * Adds a handler.
      * This implementation adds the passed handler to the end of the existing collection of handlers.
-     * @see org.eclipse.jetty.server.server.HandlerContainer#addHandler(org.eclipse.jetty.server.server.Handler)
      */
     public void addHandler(Handler handler)
     {
@@ -195,9 +189,9 @@ public class HandlerCollection extends AbstractHandlerContainer
     }
 
     /* ------------------------------------------------------------ */
-    /* Prepend a handler.
+    /**
+     * Prepends a handler.
      * This implementation adds the passed handler to the start of the existing collection of handlers.
-     * @see org.eclipse.jetty.server.server.HandlerContainer#addHandler(org.eclipse.jetty.server.server.Handler)
      */
     public void prependHandler(Handler handler)
     {
@@ -216,7 +210,6 @@ public class HandlerCollection extends AbstractHandlerContainer
         while(true)
         {
             Handlers old = _handlers.get();
-
             if (old==null || old._handlers.length==0)
                 break;
             Handlers handlers = newHandlers(ArrayUtil.removeFromArray(old._handlers, handler));
diff --git a/jetty-util/src/test/java/org/eclipse/jetty/util/thread/SerializedExecutorTest.java b/jetty-util/src/test/java/org/eclipse/jetty/util/thread/SerializedExecutorTest.java
index 9a6bab4237d..4facf1e73f4 100644
--- a/jetty-util/src/test/java/org/eclipse/jetty/util/thread/SerializedExecutorTest.java
+++ b/jetty-util/src/test/java/org/eclipse/jetty/util/thread/SerializedExecutorTest.java
@@ -30,9 +30,8 @@ import org.junit.jupiter.api.Test;
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
-class SerializedExecutorTest
+public class SerializedExecutorTest
 {
-
     @Test
     public void test() throws Exception
     {
@@ -43,19 +42,19 @@ class SerializedExecutorTest
         AtomicInteger ran = new AtomicInteger();
         AtomicBoolean running = new AtomicBoolean();
         SerializedExecutor executor = new SerializedExecutor();
-        final CountDownLatch start = new CountDownLatch(1);
-        final CountDownLatch stop = new CountDownLatch(threads);
-        final Random random = new Random();
+        CountDownLatch start = new CountDownLatch(1);
+        CountDownLatch stop = new CountDownLatch(threads);
+        Random random = new Random();
 
-        for (int t=threads; t-->0;)
+        for (int t = threads; t-- > 0; )
         {
-            new Thread(()->
+            new Thread(() ->
             {
                 try
                 {
                     start.await();
 
-                    for (int l=loops; l-->0;)
+                    for (int l = loops; l-- > 0; )
                     {
                         final AtomicInteger d = new AtomicInteger(depth);
                         executor.execute(new Runnable()
@@ -75,7 +74,7 @@ class SerializedExecutorTest
                         Thread.sleep(random.nextInt(5));
                     }
                 }
-                catch(Throwable th)
+                catch (Throwable th)
                 {
                     th.printStackTrace();
                 }
@@ -88,8 +87,6 @@ class SerializedExecutorTest
 
         start.countDown();
         assertTrue(stop.await(30, TimeUnit.SECONDS));
-        assertThat(ran.get(), Matchers.is(threads*loops*depth));
+        assertThat(ran.get(), Matchers.is(threads * loops * depth));
     }
-
-
-}
\ No newline at end of file
+}