Checkstyle fixes. (#12349)

- Added and completed JavaDocs.
- Fixed a typo in logging.
- Removed an unused parameter in a private method.

client/src/main/java/com/vaadin/client/ui/dd/DDEventHandleStrategy.java

@@ -209,6 +209,9 @@ public class DDEventHandleStrategy {
             // prevent text selection on IE
             event.getNativeEvent().preventDefault();
             return true;
+        default:
+            // NOP
+            break;
         }
         return false;
     }
@@ -272,6 +275,9 @@ public class DDEventHandleStrategy {
         case Event.ONMOUSEUP:
             handleMouseUp(targetElement, event, mediator);
             break;
+        default:
+            // NOP
+            break;
         }
     }
 
@@ -360,6 +366,9 @@ public class DDEventHandleStrategy {
      *
      * @param mediator
      *            VDragAndDropManager data accessor
+     * @param clearServerCallback
+     *            {@code true} if server communication callback should be
+     *            cleaned up, {@code false} otherwise
      */
     protected void handleDragLeave(DDManagerMediator mediator,
             boolean clearServerCallback) {

client/src/main/java/com/vaadin/client/ui/dd/DDUtil.java

@@ -22,8 +22,31 @@ import com.vaadin.client.WidgetUtil;
 import com.vaadin.shared.ui.dd.HorizontalDropLocation;
 import com.vaadin.shared.ui.dd.VerticalDropLocation;
 
+/**
+ * Utility class for drag and drop handling.
+ *
+ * @author Vaadin Ltd
+ */
 public class DDUtil {
 
+    /** Utility classes shouldn't be instantiated. */
+    private DDUtil() {
+    }
+
+    /**
+     * Get vertical drop location.
+     *
+     * @param element
+     *            the drop target element
+     * @param event
+     *            the latest {@link NativeEvent} that relates to this drag
+     *            operation
+     * @param topBottomRatio
+     *            the ratio that determines how big portion of the element on
+     *            each end counts for indicating desire to drop above or below
+     *            the element rather than on top of it
+     * @return the drop location
+     */
     public static VerticalDropLocation getVerticalDropLocation(Element element,
             NativeEvent event, double topBottomRatio) {
         int offsetHeight = element.getOffsetHeight();
@@ -31,6 +54,22 @@ public class DDUtil {
                 topBottomRatio);
     }
 
+    /**
+     * Get vertical drop location.
+     *
+     * @param element
+     *            the drop target element
+     * @param offsetHeight
+     *            the height of an element relative to the layout
+     * @param event
+     *            the latest {@link NativeEvent} that relates to this drag
+     *            operation
+     * @param topBottomRatio
+     *            the ratio that determines how big portion of the element on
+     *            each end counts for indicating desire to drop above or below
+     *            the element rather than on top of it
+     * @return the drop location
+     */
     public static VerticalDropLocation getVerticalDropLocation(Element element,
             int offsetHeight, NativeEvent event, double topBottomRatio) {
         int clientY = WidgetUtil.getTouchOrMouseClientY(event);
@@ -38,6 +77,22 @@ public class DDUtil {
                 topBottomRatio);
     }
 
+    /**
+     * Get vertical drop location.
+     *
+     * @param element
+     *            the drop target element
+     * @param offsetHeight
+     *            the height of an element relative to the layout
+     * @param clientY
+     *            the y-coordinate of the latest event that relates to this drag
+     *            operation
+     * @param topBottomRatio
+     *            the ratio that determines how big portion of the element on
+     *            each end counts for indicating desire to drop above or below
+     *            the element rather than on top of it
+     * @return the drop location
+     */
     public static VerticalDropLocation getVerticalDropLocation(Element element,
             int offsetHeight, int clientY, double topBottomRatio) {
 
@@ -57,6 +112,20 @@ public class DDUtil {
         }
     }
 
+    /**
+     * Get horizontal drop location.
+     *
+     * @param element
+     *            the drop target element
+     * @param event
+     *            the latest {@link NativeEvent} that relates to this drag
+     *            operation
+     * @param leftRightRatio
+     *            the ratio that determines how big portion of the element on
+     *            each end counts for indicating desire to drop beside the
+     *            element rather than on top of it
+     * @return the drop location
+     */
     public static HorizontalDropLocation getHorizontalDropLocation(
             Element element, NativeEvent event, double leftRightRatio) {
         int clientX = WidgetUtil.getTouchOrMouseClientX(event);

client/src/main/java/com/vaadin/client/ui/dd/VAbstractDropHandler.java

@@ -42,6 +42,7 @@ public abstract class VAbstractDropHandler implements VDropHandler {
      * details about {@link AcceptCriterion} are saved.
      *
      * @param uidl
+     *            the accept criterion UIDL
      */
     public void updateAcceptRules(UIDL uidl) {
         criterioUIDL = uidl;
@@ -107,9 +108,19 @@ public abstract class VAbstractDropHandler implements VDropHandler {
      * drag is on a valid drop location.
      *
      * @param drag
+     *            the drag event
      */
     protected abstract void dragAccepted(VDragEvent drag);
 
+    /**
+     * Validates the given drag event when all existing DnD-related tasks are
+     * completed, and triggers the callback if the validation was successful.
+     *
+     * @param cb
+     *            the callback that handles acceptance if the target is valid
+     * @param event
+     *            the drag event
+     */
     protected void validate(final VAcceptCallback cb, final VDragEvent event) {
         Command checkCriteria = () -> acceptCriteria.accept(event, criterioUIDL,
                 cb);

client/src/main/java/com/vaadin/client/ui/dd/VAcceptCallback.java

@@ -32,6 +32,9 @@ public interface VAcceptCallback {
      * icon or empahsis the target if the target accepts the transferable. If
      * the drag and drop operation ends or the {@link VAbstractDropHandler} has
      * changed before response arrives, the method is never called.
+     *
+     * @param event
+     *            the drag event
      */
     public void accepted(VDragEvent event);
 

client/src/main/java/com/vaadin/client/ui/dd/VAcceptCriteria.java

@@ -29,10 +29,21 @@ import com.vaadin.ui.dnd.DropTargetExtension;
 public class VAcceptCriteria {
     private static VAcceptCriterionFactory impl;
 
+    /** Singleton. */
+    private VAcceptCriteria() {
+    }
+
     static {
         impl = GWT.create(VAcceptCriterionFactory.class);
     }
 
+    /**
+     * Returns the accept criterion that matches the given identifier.
+     *
+     * @param name
+     *            the identifier
+     * @return the accept criterion
+     */
     public static VAcceptCriterion get(String name) {
         return impl.get(name);
     }

client/src/main/java/com/vaadin/client/ui/dd/VAcceptCriterion.java

@@ -33,8 +33,11 @@ public abstract class VAcceptCriterion {
      * transferable. If drop target is valid, callback is used.
      *
      * @param drag
+     *            the drag event
      * @param configuration
+     *            accept criterion UIDL
      * @param callback
+     *            the callback that handles acceptance if the target is valid
      */
     public void accept(final VDragEvent drag, UIDL configuration,
             final VAcceptCallback callback) {
@@ -53,8 +56,28 @@ public abstract class VAcceptCriterion {
         }
     }
 
+    /**
+     * Returns whether a client-side check accepts the drop attempt.
+     *
+     * @param drag
+     *            the drag event
+     * @param configuration
+     *            accept criterion UIDL
+     * @return {@code true} if a drop attempt is accepted, {@code false}
+     *         otherwise
+     */
     protected abstract boolean accept(VDragEvent drag, UIDL configuration);
 
+    /**
+     * Returns whether a server side check is needed for determining acceptance.
+     *
+     * @param drag
+     *            the drag event
+     * @param criterioUIDL
+     *            accept criterion UIDL
+     * @return {@code true} if a server side check is needed, {@code false}
+     *         otherwise
+     */
     public boolean needsServerSideCheck(VDragEvent drag, UIDL criterioUIDL) {
         return false;
     }

client/src/main/java/com/vaadin/client/ui/dd/VAcceptCriterionFactory.java

@@ -28,5 +28,12 @@ import com.vaadin.ui.dnd.DropTargetExtension;
 @Deprecated
 public abstract class VAcceptCriterionFactory {
 
+    /**
+     * Returns the accept criterion that matches the given identifier.
+     *
+     * @param name
+     *            the identifier
+     * @return the accept criterion
+     */
     public abstract VAcceptCriterion get(String name);
 }

client/src/main/java/com/vaadin/client/ui/dd/VDragAndDropManager.java

@@ -65,6 +65,7 @@ import com.vaadin.shared.ui.dd.DragEventType;
 @Deprecated
 public class VDragAndDropManager {
 
+    /** Style name for the active drag source. */
     public static final String ACTIVE_DRAG_SOURCE_STYLENAME = "v-active-drag-source";
 
     /**
@@ -77,11 +78,15 @@ public class VDragAndDropManager {
     public interface DDManagerMediator {
         /**
          * Returns DnD manager instance.
+         *
+         * @return the manager
          */
         VDragAndDropManager getManager();
 
         /**
          * Returns current drag event.
+         *
+         * @return the event
          */
         VDragEvent getDragEvent();
 
@@ -164,7 +169,7 @@ public class VDragAndDropManager {
         }
     }
 
-    /*
+    /**
      * #13381, #14796. The drag only actually starts when the mouse move or
      * touch move event is more than 3 pixel away.
      */
@@ -195,10 +200,16 @@ public class VDragAndDropManager {
     private DDEventHandleStrategy eventHandleStrategy;
 
     /**
-     * If dragging is currently on a drophandler, this field has reference to it
+     * If dragging is currently on a drophandler, this field has reference to
+     * it.
      */
     private VDropHandler currentDropHandler;
 
+    /**
+     * Returns the current drop handler.
+     *
+     * @return current drop handler, or {@code null} if one doesn't exist
+     */
     public VDropHandler getCurrentDropHandler() {
         return currentDropHandler;
     }
@@ -209,6 +220,7 @@ public class VDragAndDropManager {
      * .
      *
      * @param currentDropHandler
+     *            the current drop handler
      */
     public void setCurrentDropHandler(VDropHandler currentDropHandler) {
         this.currentDropHandler = currentDropHandler;
@@ -218,6 +230,12 @@ public class VDragAndDropManager {
 
     private HandlerRegistration deferredStartRegistration;
 
+    /**
+     * Returns the current drag and drop manager instance. If one doesn't exist
+     * yet, it's created.
+     *
+     * @return the current drag and drop manager
+     */
     public static VDragAndDropManager get() {
         if (instance == null) {
             instance = GWT.create(VDragAndDropManager.class);
@@ -225,7 +243,7 @@ public class VDragAndDropManager {
         return instance;
     }
 
-    /* Singleton */
+    /** Singleton. */
     protected VDragAndDropManager() {
     }
 
@@ -252,11 +270,14 @@ public class VDragAndDropManager {
      * methods on it called automatically.
      *
      * @param transferable
-     * @param nativeEvent
+     *            the VTransferable instance that represents the original
+     *            dragged element
+     * @param startEvent
+     *            the native event that starts the drag
      * @param handleDragEvents
      *            if true, {@link VDragAndDropManager} handles the drag and drop
      *            operation GWT event preview.
-     * @return
+     * @return the drag event
      */
     public VDragEvent startDrag(VTransferable transferable,
             final NativeEvent startEvent, final boolean handleDragEvents) {
@@ -400,6 +421,14 @@ public class VDragAndDropManager {
         return currentDrag;
     }
 
+    /**
+     * Updates drag image position.
+     *
+     * @param gwtEvent
+     *            the event whose coordinates should be used
+     * @param dragImage
+     *            the image to position
+     */
     protected void updateDragImagePosition(NativeEvent gwtEvent,
             Element dragImage) {
         if (gwtEvent != null && dragImage != null) {
@@ -416,7 +445,9 @@ public class VDragAndDropManager {
      * implement HasDropHandler. Returns DropHandler from that.
      *
      * @param element
-     * @return
+     *            the topmost element that is a potential drag target
+     * @return the drop handler from the given element or its closest ancestor
+     *         that has one, or {@code null} if there is no such thing
      */
     protected VDropHandler findDragTarget(Element element) {
         try {
@@ -570,6 +601,8 @@ public class VDragAndDropManager {
      * interrupted() method for cleanup.
      *
      * @param acceptCallback
+     *            the callback that should handle the matching server response
+     *            when it arrives
      */
     public void visitServer(VDragEventServerCallback acceptCallback) {
         doRequest(DragEventType.ENTER);
@@ -631,6 +664,12 @@ public class VDragAndDropManager {
 
     }
 
+    /**
+     * Handle the server response for drag and drop.
+     *
+     * @param valueMap
+     *            DnD value map from the response
+     */
     public void handleServerResponse(ValueMap valueMap) {
         if (serverCallback == null) {
             return;
@@ -721,6 +760,12 @@ public class VDragAndDropManager {
         return serverCallback != null;
     }
 
+    /**
+     * Returns the application connection for the current drag source. If there
+     * is no current drag source, returns {@code null} instead.
+     *
+     * @return the application connection, or {@code null} if not found
+     */
     protected ApplicationConnection getCurrentDragApplicationConnection() {
         if (currentDrag == null) {
             return null;
@@ -754,6 +799,7 @@ public class VDragAndDropManager {
      * command in queue here.
      *
      * @param command
+     *            the command to execute
      */
     public void executeWhenReady(Command command) {
         if (isBusy()) {

client/src/main/java/com/vaadin/client/ui/dd/VDragEvent.java

@@ -66,21 +66,35 @@ public class VDragEvent {
         id = eventId++;
     }
 
+    /**
+     * Returns the VTransferable instance that represents the original dragged
+     * element.
+     *
+     * @return the transferable instance
+     */
     public VTransferable getTransferable() {
         return transferable;
     }
 
     /**
-     * Returns the the latest {@link NativeEvent} that relates to this drag and
-     * drop operation. For example on {@link VDropHandler#dragEnter(VDragEvent)}
-     * this is commonly a {@link MouseOverEvent}.
+     * Returns the latest {@link NativeEvent} that relates to this drag and drop
+     * operation. For example on {@link VDropHandler#dragEnter(VDragEvent)} this
+     * is commonly a {@link MouseOverEvent}.
      *
-     * @return
+     * @return the latest event
      */
     public NativeEvent getCurrentGwtEvent() {
         return currentGwtEvent;
     }
 
+    /**
+     * Sets the latest {@link NativeEvent} that relates to this drag and drop
+     * operation. For example on {@link VDropHandler#dragEnter(VDragEvent)} this
+     * is commonly a {@link MouseOverEvent}.
+     *
+     * @param event
+     *            the latest event
+     */
     public void setCurrentGwtEvent(NativeEvent event) {
         currentGwtEvent = event;
     }
@@ -114,6 +128,9 @@ public class VDragEvent {
     /**
      * @deprecated As of 7.2, call or override {@link #setElementOver(Element)}
      *             instead
+     * @param targetElement
+     *            target element over which DnD event has happened
+     * @see #getElementOver()
      */
     @Deprecated
     public void setElementOver(
@@ -123,6 +140,9 @@ public class VDragEvent {
 
     /**
      * @since 7.2
+     * @param targetElement
+     *            target element over which DnD event has happened
+     * @see #getElementOver()
      */
     public void setElementOver(Element targetElement) {
         setElementOver(DOM.asOld(targetElement));
@@ -142,6 +162,9 @@ public class VDragEvent {
      * to HTML5 DataTransfer
      *
      * @param node
+     *            a cloned node or other representation of the original element
+     *            that is dragged
+     *
      * @deprecated As of 7.2, call or override {@link #setDragImage(Element)}
      *             instead
      */
@@ -164,6 +187,8 @@ public class VDragEvent {
      * to HTML5 DataTransfer
      *
      * @param node
+     *            a cloned node or other representation of the original element
+     *            that is dragged
      *
      * @since 7.2
      */
@@ -178,7 +203,7 @@ public class VDragEvent {
      *
      * TODO clean up when drop handler changes
      *
-     * @return
+     * @return the drop details
      */
     public Map<String, Object> getDropDetails() {
         return dropDetails;
@@ -241,6 +266,7 @@ public class VDragEvent {
      * Automatically tries to create a proxy image from given element.
      *
      * @param element
+     *            the original element that is dragged
      * @param alignImageToEvent
      *            if true, proxy image is aligned to start event, else next to
      *            mouse cursor
@@ -284,6 +310,7 @@ public class VDragEvent {
      * Automatically tries to create a proxy image from given element.
      *
      * @param element
+     *            the original element that is dragged
      * @param alignImageToEvent
      *            if true, proxy image is aligned to start event, else next to
      *            mouse cursor

client/src/main/java/com/vaadin/client/ui/dd/VDragEventServerCallback.java

@@ -26,6 +26,14 @@ import com.vaadin.shared.ui.dnd.DropTargetRpc;
 @Deprecated
 public interface VDragEventServerCallback {
 
+    /**
+     * Handle the server response for drag and drop.
+     *
+     * @param accepted
+     *            {@code true} if the target accepts the transferable
+     * @param response
+     *            DnD data within the server response
+     */
     public void handleResponse(boolean accepted, UIDL response);
 
 }

client/src/main/java/com/vaadin/client/ui/dd/VDropHandler.java

@@ -73,11 +73,14 @@ public interface VDropHandler {
      * though mouse is not moved.
      *
      * @param currentDrag
+     *            the latest drag event
      */
     public void dragOver(VDragEvent currentDrag);
 
     /**
      * Returns the ComponentConnector with which this DropHandler is associated.
+     *
+     * @return the connector
      */
     public ComponentConnector getConnector();
 
@@ -85,6 +88,8 @@ public interface VDropHandler {
      * Returns the application connection to which this {@link VDropHandler}
      * belongs to. DragAndDropManager uses this function to send Transferable to
      * server side.
+     *
+     * @return the application connection
      */
     public ApplicationConnection getApplicationConnection();
 

client/src/main/java/com/vaadin/client/ui/dd/VHasDropHandler.java

@@ -29,5 +29,10 @@ import com.vaadin.client.extensions.DropTargetExtensionConnector;
  */
 @Deprecated
 public interface VHasDropHandler {
+    /**
+     * Returns the drop handler for this widget.
+     *
+     * @return the drop handler
+     */
     public VDropHandler getDropHandler();
 }

client/src/main/java/com/vaadin/client/ui/dd/VHtml5DragEvent.java

@@ -28,15 +28,29 @@ import com.vaadin.client.extensions.DropTargetExtensionConnector;
  */
 @Deprecated
 public class VHtml5DragEvent extends NativeEvent {
+    /** Singleton. */
     protected VHtml5DragEvent() {
     }
 
+    /**
+     * Returns type values, or {@code ["Text","Url","Html"]} if types are not
+     * supported.
+     *
+     * @return types
+     */
     public final native JsArrayString getTypes()
     /*-{
         // IE does not support types, return some basic values
         return this.dataTransfer.types ? this.dataTransfer.types : ["Text","Url","Html"];
      }-*/;
 
+    /**
+     * Returns the data for the given type as text.
+     *
+     * @param type
+     *            the type whose data to retrieve
+     * @return the data as text
+     */
     public final native String getDataAsText(String type)
     /*-{
          var v = this.dataTransfer.getData(type);
@@ -47,8 +61,11 @@ public class VHtml5DragEvent extends NativeEvent {
      * Works on FF 3.6 and possibly with gears.
      *
      * @param index
-     * @return
+     *            the index of the file to get
+     * @return the file as text
+     * @deprecated this method is no longer used internally
      */
+    @Deprecated
     public final native String getFileAsString(int index)
     /*-{
         if (this.dataTransfer.files.length > 0 && this.dataTransfer.files[0].getAsText) {
@@ -57,6 +74,12 @@ public class VHtml5DragEvent extends NativeEvent {
         return null;
     }-*/;
 
+    /**
+     * Sets the drop effect value.
+     *
+     * @param effect
+     *            the drop effect
+     */
     public final native void setDropEffect(String effect)
     /*-{
         try {
@@ -64,21 +87,45 @@ public class VHtml5DragEvent extends NativeEvent {
         } catch (e) {}
      }-*/;
 
+    /**
+     * Returns whether drop effect is allowed or not.
+     *
+     * @return {@code true} id drop effect is allowed, {@code false} otherwise
+     */
     public final native String getEffectAllowed()
     /*-{
             return this.dataTransfer.effectAllowed;
      }-*/;
 
+    /**
+     * Sets whether drop effect is allowed or not.
+     *
+     * @param effect
+     *            {@code true} id drop effect should be allowed, {@code false}
+     *            otherwise
+     */
     public final native void setEffectAllowed(String effect)
     /*-{
             this.dataTransfer.effectAllowed = effect;
      }-*/;
 
+    /**
+     * Returns the transfer file count.
+     *
+     * @return the file count
+     */
     public final native int getFileCount()
     /*-{
             return this.dataTransfer.files ? this.dataTransfer.files.length : 0;
      }-*/;
 
+    /**
+     * Returns the file indicated by the given index.
+     *
+     * @param fileIndex
+     *            the index of the file
+     * @return the file
+     */
     public final native VHtml5File getFile(int fileIndex)
     /*-{
             return this.dataTransfer.files[fileIndex];
@@ -88,6 +135,11 @@ public class VHtml5DragEvent extends NativeEvent {
      * Detects if dropped element is a file. <br>
      * Always returns <code>true</code> on Safari even if the dropped element is
      * a folder.
+     *
+     * @param fileIndex
+     *            the index of the element to check
+     * @return {@code true} if the dropped element is a file, {@code false}
+     *         otherwise
      */
     public final native boolean isFile(int fileIndex)
     /*-{
@@ -113,6 +165,14 @@ public class VHtml5DragEvent extends NativeEvent {
         return true;
     }-*/;
 
+    /**
+     * Adds a data String with the given flavor identifier.
+     *
+     * @param flavor
+     *            the identifier
+     * @param data
+     *            the data
+     */
     public final native void setHtml5DataFlavor(String flavor, String data)
     /*-{
         this.dataTransfer.setData(flavor, data);

client/src/main/java/com/vaadin/client/ui/dd/VHtml5File.java

@@ -28,24 +28,37 @@ import com.google.gwt.core.client.JavaScriptObject;
 @Deprecated
 public class VHtml5File extends JavaScriptObject {
 
+    /** Singleton. */
     protected VHtml5File() {
     }
 
+    /**
+     * Returns the name value.
+     *
+     * @return the name
+     */
     public final native String getName()
     /*-{
         return this.name;
      }-*/;
 
+    /**
+     * Returns the type value.
+     *
+     * @return the type
+     */
     public final native String getType()
     /*-{
         return this.type;
      }-*/;
 
-    /*
+    /**
      * Browser implementations support files >2GB dropped and report the value
      * as long. Due to JSNI limitations this value needs to be sent as double
      * and then cast back to a long value.
      * www.gwtproject.org/doc/latest/DevGuideCodingBasicsJSNI.html#important
+     *
+     * @return the size
      */
     public final native double getSize()
     /*-{

client/src/main/java/com/vaadin/client/ui/dd/VNot.java

@@ -38,9 +38,9 @@ public final class VNot extends VAcceptCriterion {
     public void accept(VDragEvent drag, UIDL configuration,
             VAcceptCallback callback) {
         if (crit1 == null) {
-            crit1 = getCriteria(drag, configuration, 0);
+            crit1 = getCriteria(configuration, 0);
             if (crit1 == null) {
-                getLogger().info("Not criteria didn't found a child criteria");
+                getLogger().info("Not criteria didn't find a child criteria");
                 return;
             }
         }
@@ -55,8 +55,7 @@ public final class VNot extends VAcceptCriterion {
         }
     }
 
-    private VAcceptCriterion getCriteria(VDragEvent drag, UIDL configuration,
-            int i) {
+    private VAcceptCriterion getCriteria(UIDL configuration, int i) {
         UIDL childUIDL = configuration.getChildUIDL(i);
         return VAcceptCriteria.get(childUIDL.getStringAttribute("name"));
     }

client/src/main/java/com/vaadin/client/ui/dd/VTransferable.java

@@ -61,14 +61,42 @@ public class VTransferable {
         this.component = component;
     }
 
+    /**
+     * Returns previously saved data that is referred to by the given
+     * identifier.
+     *
+     * @param dataFlavor
+     *            the identifier for the data object
+     * @return the data object, or {@code null} if not found
+     *
+     * @see #setData(String, Object)
+     */
     public Object getData(String dataFlavor) {
         return variables.get(dataFlavor);
     }
 
+    /**
+     * Stores any type of named data that can be useful during the DnD
+     * operation.
+     *
+     * @param dataFlavor
+     *            the identifier for the data object, should not be {@code null}
+     * @param value
+     *            the data to store, should not be {@code null}
+     */
     public void setData(String dataFlavor, Object value) {
         variables.put(dataFlavor, value);
     }
 
+    /**
+     * Returns a collection of stored identifiers that each correspond with one
+     * stored data object.
+     *
+     * @return the collection of identifiers, can be empty if no data has been
+     *         stored yet
+     *
+     * @see #setData(String, Object)
+     */
     public Collection<String> getDataFlavors() {
         return variables.keySet();
     }

client/src/main/java/com/vaadin/client/ui/draganddropwrapper/DragAndDropWrapperConnector.java

@@ -35,6 +35,7 @@ import com.vaadin.shared.ui.draganddropwrapper.DragAndDropWrapperServerRpc;
 import com.vaadin.ui.DragAndDropWrapper;
 
 /**
+ * A connector class for the DragAndDropWrapper.
  *
  * @author Vaadin Ltd
  * @deprecated Replaced in 8.1 with {@link DragSourceExtensionConnector} and