Use Collection.isEmpty() (#10172)

client/src/main/java/com/vaadin/client/componentlocator/ComponentLocator.java

         for (LocatorStrategy strategy : locatorStrategies) {
             if (strategy.validatePath(path)) {
                 List<Element> elements = strategy.getElementsByPath(path);
-                if (elements.size() > 0) {
+                if (!elements.isEmpty()) {
                     for (Element e : elements) {
                         jsElements.push(e);
                     }
             if (strategy.validatePath(path)) {
                 List<Element> elements = strategy
                         .getElementsByPathStartingAt(path, root);
-                if (elements.size() > 0) {
+                if (!elements.isEmpty()) {
                     for (Element e : elements) {
                         jsElements.push(e);
                     }

client/src/main/java/com/vaadin/client/componentlocator/VaadinFinderLocatorStrategy.java

             path.add(pathFragment);
         }
 
-        if (path.size() == 0) {
+        if (path.isEmpty()) {
             // If we didn't find a single element, return null..
             return null;
         }
     public List<Element> getElementsByPath(String path) {
         List<SelectorPredicate> postFilters = SelectorPredicate
                 .extractPostFilterPredicates(path);
-        if (postFilters.size() > 0) {
+        if (!postFilters.isEmpty()) {
             path = path.substring(1, path.lastIndexOf(')'));
         }
 
             Element root) {
         List<SelectorPredicate> postFilters = SelectorPredicate
                 .extractPostFilterPredicates(path);
-        if (postFilters.size() > 0) {
+        if (!postFilters.isEmpty()) {
             path = path.substring(1, path.lastIndexOf(')'));
         }
 
         List<Integer> widgetTags = new ArrayList<>();
         widgetTags.addAll(getTags(widgetName));
 
-        if (widgetTags.size() == 0) {
+        if (widgetTags.isEmpty()) {
             widgetTags.addAll(getTags("com.vaadin.ui." + widgetName));
         }
 
             final String simpleName = getSimpleClassName(name);
             final String fullName = getFullClassName(name);
 
-            if (widgetTags.size() > 0) {
+            if (!widgetTags.isEmpty()) {
                 Integer[] foundTags = client.getConfiguration()
                         .getTagsForServerSideClassName(fullName);
                 for (int tag : foundTags) {

client/src/main/java/com/vaadin/client/connectors/grid/GridDragSourceConnector.java

         draggedItems = getDraggedRows(nativeEvent);
 
         // Ignore event if there are no items dragged
-        if (draggedItems.size() == 0) {
+        if (draggedItems.isEmpty()) {
             return;
         }
 
             final Element selectionColumnCell = getGrid().getSelectionColumn()
                     .isPresent()
                     // -1 is used when even selection column is not frozen
-                    && frozenColumnCount != -1 ? draggedRowElement
-                            .removeChild(draggedRowElement.getFirstChild())
-                            .cast() : null;
+                    && frozenColumnCount != -1
+                            ? draggedRowElement
+                                    .removeChild(
+                                            draggedRowElement.getFirstChild())
+                                    .cast()
+                            : null;
 
             final List<String> frozenCellsTransforms = new ArrayList<>();
             for (int i = 0; i < getGrid().getColumnCount(); i++) {
             return;
         }
         // Ignore event if there are no items dragged
-        if (draggedItems != null && draggedItems.size() > 0) {
+        if (draggedItems != null && !draggedItems.isEmpty()) {
             super.onDragEnd(event);
         }
 
      * @return Stream of dragged table row elements.
      */
     private Stream<TableRowElement> getDraggedRowElementStream() {
-        return draggedItems.stream()
-                .map(row -> ((AbstractRemoteDataSource<JsonObject>) gridConnector
+        return draggedItems.stream().map(
+                row -> ((AbstractRemoteDataSource<JsonObject>) gridConnector
                         .getDataSource()).indexOf(row))
                 .map(getGridBody()::getRowElement);
     }

client/src/main/java/com/vaadin/client/debug/internal/AnalyzeLayoutsPanel.java

         Set<ComponentConnector> zeroWidthComponents = new HashSet<>();
         findZeroSizeComponents(zeroHeightComponents, zeroWidthComponents,
                 ac.getUIConnector());
-        if (zeroHeightComponents.size() > 0 || zeroWidthComponents.size() > 0) {
+        if (!zeroHeightComponents.isEmpty() || !zeroWidthComponents.isEmpty()) {
             add(new HTML("<h4> Client side notifications</h4>"
                     + " <em>The following relative sized components were "
                     + "rendered to a zero size container on the client side."
                     + " Note that these are not necessarily invalid "
                     + "states, but reported here as they might be.</em>"));
-            if (zeroHeightComponents.size() > 0) {
+            if (!zeroHeightComponents.isEmpty()) {
                 add(new HTML("<p><strong>Vertically zero size:</strong></p>"));
                 printClientSideDetectedIssues(zeroHeightComponents, ac);
             }
-            if (zeroWidthComponents.size() > 0) {
+            if (!zeroWidthComponents.isEmpty()) {
                 add(new HTML(
                         "<p><strong>Horizontally zero size:</strong></p>"));
                 printClientSideDetectedIssues(zeroWidthComponents, ac);

client/src/main/java/com/vaadin/client/debug/internal/InfoSection.java

         clear();
         List<ApplicationConnection> apps = ApplicationConfiguration
                 .getRunningApplications();
-        if (apps.size() == 0) {
+        if (apps.isEmpty()) {
             // try again in a while
             refresher.schedule(1000);
         } else {

client/src/main/java/com/vaadin/client/debug/internal/SelectorPath.java

         String tmpPath = path;
         List<SelectorPredicate> postFilters = SelectorPredicate
                 .extractPostFilterPredicates(path);
-        if (postFilters.size() > 0) {
+        if (!postFilters.isEmpty()) {
             tmpPath = tmpPath.substring(1, tmpPath.lastIndexOf(')'));
             if (tmpPath.contains("#")) {
                 // FIXME: SubParts should be handled.

client/src/main/java/com/vaadin/client/extensions/FileDropTargetConnector.java

      */
     private void uploadNextFile() {
         Scheduler.get().scheduleDeferred(() -> {
-            if (!uploading && uploadUrls.size() > 0) {
+            if (!uploading && !uploadUrls.isEmpty()) {
                 uploading = true;
                 String nextId = uploadUrls.keySet().stream().findAny().get();
 
             }
 
             // Request a list of upload URLs for the dropped files
-            if (fileParams.size() > 0) {
+            if (!fileParams.isEmpty()) {
                 getRpcProxy(FileDropTargetRpc.class).drop(fileParams);
             }
 
         protected FileUploadXHR() {
         }
 
-        public final native void postFile(File file) /*-{
+        public final native void postFile(File file)
+        /*-{
             this.setRequestHeader('Content-Type', 'multipart/form-data');
             this.send(file);
         }-*/;

client/src/main/java/com/vaadin/client/extensions/ResponsiveConnector.java

         selectors.append('.').append(primaryStyle);
 
         if (target.getState().styles != null
-                && target.getState().styles.size() > 0) {
+                && !target.getState().styles.isEmpty()) {
             for (String style : target.getState().styles) {
                 selectors.append(",.").append(style);
                 selectors.append(",.").append(primaryStyle).append('.')

client/src/main/java/com/vaadin/client/ui/VComboBox.java

          * Gets the preferred height of the menu including pageItemsCount items.
          */
         String getPreferredHeight(int pageItemsCount) {
-            if (currentSuggestions.size() > 0) {
+            if (!currentSuggestions.isEmpty()) {
                 final int pixels = getPreferredHeight()
                         / currentSuggestions.size() * pageItemsCount;
                 return pixels + "px";
          */
         int getItemOffsetHeight() {
             List<MenuItem> items = getItems();
-            return items != null && items.size() > 0
+            return items != null && !items.isEmpty()
                     ? items.get(0).getOffsetHeight()
                     : 0;
         }
          */
         int getItemOffsetWidth() {
             List<MenuItem> items = getItems();
-            return items != null && items.size() > 0
+            return items != null && !items.isEmpty()
                     ? items.get(0).getOffsetWidth()
                     : 0;
         }

client/src/main/java/com/vaadin/client/ui/VDragAndDropWrapper.java

             @Override
             public void execute() {
                 if (!uploading) {
-                    if (fileIds.size() > 0) {
+                    if (!fileIds.isEmpty()) {
 
                         uploading = true;
                         final Integer fileId = fileIds.remove(0);

client/src/main/java/com/vaadin/client/ui/VMenuBar.java

         // Only collapse if there is more than one item in the root menu and the
         // menu has an explicit size
         if ((getItems().size() > 1 || (collapsedRootItems != null
-                && collapsedRootItems.getItems().size() > 0))
+                && !collapsedRootItems.getItems().isEmpty()))
                 && getElement().getStyle().getProperty("width") != null
                 && moreItem != null) {
 
                 }
                 int widthReduced = 0;
 
-                while (widthReduced < widthNeeded && getItems().size() > 0) {
+                while (widthReduced < widthNeeded && !getItems().isEmpty()) {
                     // Move last root menu item to collapsed menu
                     CustomMenuItem collapse = getItems()
                             .get(getItems().size() - 1);
                     removeItem(collapse);
                     collapsedRootItems.addItem(collapse, 0);
                 }
-            } else if (collapsedRootItems.getItems().size() > 0) {
+            } else if (!collapsedRootItems.getItems().isEmpty()) {
                 // Space available for items: expand first items from collapsed
                 // menu
                 int widthAvailable = diff + moreItemWidth;
                 int widthGrowth = 0;
 
                 while (widthAvailable > widthGrowth
-                        && collapsedRootItems.getItems().size() > 0) {
+                        && !collapsedRootItems.getItems().isEmpty()) {
                     // Move first item from collapsed menu to the root menu
                     CustomMenuItem expand = collapsedRootItems.getItems()
                             .get(0);
                     collapsedRootItems.removeItem(expand);
                     addItem(expand);
                     widthGrowth += expand.getOffsetWidth();
-                    if (collapsedRootItems.getItems().size() > 0) {
+                    if (!collapsedRootItems.getItems().isEmpty()) {
                         widthAvailable -= moreItemWidth;
                     }
                     if (widthGrowth > widthAvailable) {
                     }
                 }
             }
-            if (collapsedRootItems.getItems().size() > 0) {
+            if (!collapsedRootItems.getItems().isEmpty()) {
                 addItem(moreItem);
             }
         }

client/src/main/java/com/vaadin/client/ui/VWindow.java

     }
 
     private static VWindow getTopmostWindow() {
-        if (windowOrder.size() > 0) {
+        if (!windowOrder.isEmpty()) {
             return windowOrder.get(windowOrder.size() - 1);
         }
         return null;

client/src/main/java/com/vaadin/client/ui/menubar/MenuBar.java

      * @return the first item from the menu or null if no items.
      */
     public MenuItem getFirstItem() {
-        return items != null && items.size() > 0 ? items.get(0) : null;
+        return items != null && !items.isEmpty() ? items.get(0) : null;
     }
 
     /**
      * @return the last item from the menu or null if no items.
      */
     public MenuItem getLastItem() {
-        return items != null && items.size() > 0 ? items.get(items.size() - 1)
+        return items != null && !items.isEmpty() ? items.get(items.size() - 1)
                 : null;
     }
 
      */
     private void onShow() {
         // Select the first item when a menu is shown.
-        if (items.size() > 0) {
+        if (!items.isEmpty()) {
             selectItem(items.get(0));
         }
     }

client/src/main/java/com/vaadin/client/widget/grid/datasources/ListSorter.java

 
                     if (result != 0) {
                         return o.getDirection() == SortDirection.ASCENDING
-                                ? result : -result;
+                                ? result
+                                : -result;
                     }
                 }
 
-                if (order.size() > 0) {
+                if (!order.isEmpty()) {
                     return order.get(0)
                             .getDirection() == SortDirection.ASCENDING
                                     ? a.hashCode() - b.hashCode()

client/src/main/java/com/vaadin/client/widgets/Escalator.java

                         velocity = delta / ellapsed;
                         // if last speed was so low, reset speeds and start
                         // storing again
-                        if (speeds.size() > 0 && !validSpeed(speeds.get(0))) {
+                        if (!speeds.isEmpty() && !validSpeed(speeds.get(0))) {
                             speeds.clear();
                             run = true;
                         }

compatibility-client/src/main/java/com/vaadin/v7/client/ui/VFilterSelect.java

          * Gets the preferred height of the menu including pageItemsCount items.
          */
         String getPreferredHeight(int pageItemsCount) {
-            if (currentSuggestions.size() > 0) {
+            if (!currentSuggestions.isEmpty()) {
                 final int pixels = (getPreferredHeight()
                         / currentSuggestions.size()) * pageItemsCount;
                 return pixels + "px";
          */
         int getItemOffsetHeight() {
             List<MenuItem> items = getItems();
-            return items != null && items.size() > 0
+            return items != null && !items.isEmpty()
                     ? items.get(0).getOffsetHeight()
                     : 0;
         }
          */
         int getItemOffsetWidth() {
             List<MenuItem> items = getItems();
-            return items != null && items.size() > 0
+            return items != null && !items.isEmpty()
                     ? items.get(0).getOffsetWidth()
                     : 0;
         }

compatibility-client/src/main/java/com/vaadin/v7/client/ui/VScrollTable.java

             // that is the same as the previous selection. This prevents
             // unwanted scrolling (#18247).
             boolean rowsUnSelected = removeUnselectedRowKeys(selectedKeys);
-            boolean updateFocus = rowsUnSelected || selectedRowKeys.size() == 0
+            boolean updateFocus = rowsUnSelected || selectedRowKeys.isEmpty()
                     || focusedRow == null;
             if (scrollBody != null) {
                 for (Widget w : scrollBody) {

compatibility-client/src/main/java/com/vaadin/v7/client/ui/VTree.java

     public void setSelected(TreeNode treeNode, boolean selected) {
         if (selected) {
             if (!isMultiselect) {
-                while (selectedIds.size() > 0) {
+                while (!selectedIds.isEmpty()) {
                     final String id = selectedIds.iterator().next();
                     final TreeNode oldSelection = getNodeByKey(id);
                     if (oldSelection != null) {
             TreeNode node = null;
             // If node is open and has children then move in to the children
             if (!focusedNode.isLeaf() && focusedNode.getState()
-                    && focusedNode.getChildren().size() > 0) {
+                    && !focusedNode.getChildren().isEmpty()) {
                 node = focusedNode.getChildren().get(0);
             } else {
                 // Move down to the next sibling
      * @return The bottom most child
      */
     private TreeNode getLastVisibleChildInTree(TreeNode root) {
-        if (root.isLeaf() || !root.getState()
-                || root.getChildren().size() == 0) {
+        if (root.isLeaf() || !root.getState() || root.getChildren().isEmpty()) {
             return root;
         }
         List<TreeNode> children = root.getChildren();

compatibility-client/src/main/java/com/vaadin/v7/client/ui/table/TableConnector.java

                     // in selection and exists with same index
                     getWidget().setRowFocus(getWidget().getRenderedRowByKey(
                             getWidget().focusedRow.getKey()));
-                } else if (getWidget().selectedRowKeys.size() > 0) {
+                } else if (!getWidget().selectedRowKeys.isEmpty()) {
                     // try to focus any row in selection
                     getWidget().setRowFocus(getWidget().getRenderedRowByKey(
                             getWidget().selectedRowKeys.iterator().next()));

compatibility-client/src/main/java/com/vaadin/v7/client/widget/grid/datasources/ListSorter.java

 
                     if (result != 0) {
                         return o.getDirection() == SortDirection.ASCENDING
-                                ? result : -result;
+                                ? result
+                                : -result;
                     }
                 }
 
-                if (order.size() > 0) {
+                if (!order.isEmpty()) {
                     return order.get(0)
                             .getDirection() == SortDirection.ASCENDING
                                     ? a.hashCode() - b.hashCode()

compatibility-client/src/main/java/com/vaadin/v7/client/widget/grid/selection/SelectionModelMulti.java

 
     @Override
     public boolean deselectAll() {
-        if (selectedRows.size() > 0) {
+        if (!selectedRows.isEmpty()) {
 
             @SuppressWarnings("unchecked")
             final LinkedHashSet<RowHandle<T>> selectedRowsClone = (LinkedHashSet<RowHandle<T>>) selectedRows
             }
         }
 
-        if (added.size() > 0) {
+        if (!added.isEmpty()) {
             grid.fireEvent(new SelectionEvent<T>(grid, added, null,
                     isBeingBatchSelected()));
 
             }
         }
 
-        if (removed.size() > 0) {
+        if (!removed.isEmpty()) {
             grid.fireEvent(new SelectionEvent<T>(grid, null, removed,
                     isBeingBatchSelected()));
             return true;

compatibility-client/src/main/java/com/vaadin/v7/client/widgets/Escalator.java

                         velocity = delta / ellapsed;
                         // if last speed was so low, reset speeds and start
                         // storing again
-                        if (speeds.size() > 0 && !validSpeed(speeds.get(0))) {
+                        if (!speeds.isEmpty() && !validSpeed(speeds.get(0))) {
                             speeds.clear();
                             run = true;
                         }

compatibility-server/src/main/java/com/vaadin/v7/data/validator/BeanValidator.java

  * @author Petri Hakala
  * @author Henri Sara
  *
- * @deprecated See {@link BeanValidationBinder} and {@link com.vaadin.data.validator.BeanValidator}
+ * @deprecated See {@link BeanValidationBinder} and
+ *             {@link com.vaadin.data.validator.BeanValidator}
  */
 @Deprecated
 public class BeanValidator implements Validator {
     public void validate(final Object value) throws InvalidValueException {
         Set<?> violations = getJavaxBeanValidator().validateValue(beanClass,
                 propertyName, value);
-        if (violations.size() > 0) {
+        if (!violations.isEmpty()) {
             InvalidValueException[] causes = new InvalidValueException[violations
                     .size()];
             int i = 0;

compatibility-server/src/main/java/com/vaadin/v7/ui/AbstractSelect.java

                     }
                 }
 
-                if (!isNullSelectionAllowed()
-                        && acceptedSelections.size() < 1) {
+                if (!isNullSelectionAllowed() && acceptedSelections.isEmpty()) {
                     // empty selection not allowed, keep old value
                     markAsDirty();
                     return;

compatibility-server/src/main/java/com/vaadin/v7/ui/Form.java

      */
     private Field<?> getFirstFocusableField() {
         Collection<?> itemPropertyIds = getItemPropertyIds();
-        if (itemPropertyIds != null && itemPropertyIds.size() > 0) {
+        if (itemPropertyIds != null && !itemPropertyIds.isEmpty()) {
             for (Object id : itemPropertyIds) {
                 if (id != null) {
                     Field<?> field = getField(id);

compatibility-server/src/main/java/com/vaadin/v7/ui/Grid.java

             protected void readDesign(Element cellElement,
                     DesignContext designContext) {
                 if (!cellElement.hasAttr("plain-text")) {
-                    if (cellElement.children().size() > 0
+                    if (!cellElement.children().isEmpty()
                             && cellElement.child(0).tagName().contains("-")) {
                         setComponent(
                                 designContext.readDesign(cellElement.child(0)));
          */
         protected void readDesign(Element tableSectionElement,
                 DesignContext designContext) throws DesignException {
-            while (rows.size() > 0) {
+            while (!rows.isEmpty()) {
                 removeRow(0);
             }
 
                     "selection-mode", attrs, SelectionMode.class));
         }
 
-        if (design.children().size() > 0) {
+        if (!design.children().isEmpty()) {
             if (design.children().size() > 1
                     || !design.child(0).tagName().equals("table")) {
                 throw new DesignException(

compatibility-server/src/main/java/com/vaadin/v7/ui/Tree.java

             }
         }
 
-        if (!isNullSelectionAllowed() && s.size() < 1) {
+        if (!isNullSelectionAllowed() && s.isEmpty()) {
             // empty selection not allowed, keep old value
             markAsDirty();
             return;

compatibility-server/src/main/java/com/vaadin/v7/ui/TreeTable.java

 
         @Override
         public Object lastItemId() {
-            if (getPreOrder().size() > 0) {
+            if (!getPreOrder().isEmpty()) {
                 return getPreOrder().get(getPreOrder().size() - 1);
             } else {
                 return null;

compatibility-server/src/test/java/com/vaadin/v7/data/util/AbstractHierarchicalContainerTestBase.java

                 Collection<?> children = container.getChildren(rootId);
                 assertNotNull(rootId + " should have children", children);
                 assertTrue(rootId + " should have children",
-                        (children.size() > 0));
+                        !children.isEmpty());
                 // getParent
                 for (Object childId : children) {
                     assertEquals(container.getParent(childId), rootId);
         if (!container.areChildrenAllowed(itemId)) {
             // If no children is allowed the item should have no children
             assertFalse(container.hasChildren(itemId));
-            assertTrue(children == null || children.size() == 0);
+            assertTrue(children == null || children.isEmpty());
 
             return;
         }

compatibility-server/src/test/java/com/vaadin/v7/tests/server/component/table/TablePropertyValueConverterTest.java

     @Test
     public void testRemovePropertyId() {
         Collection<Object> converters = table.getCurrentConverters();
-        assertTrue("Set of converters was empty at the start.",
-                converters.size() > 0);
+        assertFalse("Set of converters was empty at the start.",
+                converters.isEmpty());
 
         Object firstId = converters.iterator().next();
 
             }
         });
         Set<Object> converters = customTable.getCurrentConverters();
-        assertTrue("Converter was not set.", converters.size() > 0);
+        assertFalse("Converter was not set.", converters.isEmpty());
     }
 
     @Test

server/src/main/java/com/vaadin/data/provider/DataCommunicator.java

 
             List<T> rowsToPush = fetchItemsWithRange(offset, limit);
 
-            if (!initial && !reset && rowsToPush.size() == 0) {
+            if (!initial && !reset && rowsToPush.isEmpty()) {
                 triggerReset = true;
             }
 

server/src/main/java/com/vaadin/server/AbstractClientConnector.java

 
         Collection<Extension> extensions = connector.getExtensions();
         boolean hasComponents = connector instanceof HasComponents;
-        boolean hasExtensions = extensions.size() > 0;
+        boolean hasExtensions = !extensions.isEmpty();
         if (!hasComponents && !hasExtensions) {
             // If has neither component nor extensions, return immutable empty
             // list as iterable.

server/src/main/java/com/vaadin/server/AbstractErrorMessage.java

             break;
         }
         // if no message, combine the messages of all children
-        if (null == result && null != getCauses() && getCauses().size() > 0) {
+        if (null == result && null != getCauses() && !getCauses().isEmpty()) {
             StringBuilder sb = new StringBuilder();
             for (ErrorMessage cause : getCauses()) {
                 String childMessage = cause.getFormattedHtmlMessage();

server/src/main/java/com/vaadin/server/ComponentSizeValidator.java

                 clientJSON.append(",\"widthMsg\":\"").append(msg).append("\"");
                 printServerError(msg, attributes, true, serverErrorStream);
             }
-            if (subErrors.size() > 0) {
+            if (!subErrors.isEmpty()) {
                 serverErrorStream.println("Sub errors >>");
                 clientJSON.append(", \"subErrors\" : [");
                 boolean first = true;

server/src/main/java/com/vaadin/server/JsonPaintTarget.java

                     "Attempted to write to a closed PaintTarget.");
         }
 
-        if (openJsonTags.size() > 0) {
+        if (!openJsonTags.isEmpty()) {
             final JsonTag parent = openJsonTags.pop();
 
             String lastTag = "";

server/src/main/java/com/vaadin/ui/DragAndDropWrapper.java

         if (getDropHandler() != null) {
             getDropHandler().getAcceptCriterion().paint(target);
         }
-        if (receivers != null && receivers.size() > 0) {
+        if (receivers != null && !receivers.isEmpty()) {
             for (Iterator<Entry<String, ProxyReceiver>> it = receivers
                     .entrySet().iterator(); it.hasNext();) {
                 Entry<String, ProxyReceiver> entry = it.next();

server/src/main/java/com/vaadin/ui/GridLayout.java

                 Element col = cols.get(column);
                 Component child = null;
 
-                if (col.children().size() > 0) {
+                if (!col.children().isEmpty()) {
                     Element childElement = col.child(0);
                     child = designContext.readDesign(childElement);
                     alignments.put(child, DesignAttributeHandler

server/src/main/java/com/vaadin/ui/components/grid/StaticSection.java

         protected void readDesign(Element cellElement,
                 DesignContext designContext) {
             if (!cellElement.hasAttr("plain-text")) {
-                if (cellElement.children().size() > 0
+                if (!cellElement.children().isEmpty()
                         && cellElement.child(0).tagName().contains("-")) {
                     setComponent(
                             designContext.readDesign(cellElement.child(0)));

server/src/main/java/com/vaadin/ui/declarative/FieldBinder.java

                 throw new FieldBindingException("Could not get field value", e);
             }
         }
-        if (unboundFields.size() > 0) {
+        if (!unboundFields.isEmpty()) {
             getLogger().severe(
                     "Found unbound fields in component root :" + unboundFields);
         }

server/src/main/java/com/vaadin/ui/dnd/FileDropTarget.java

 
         // Send upload URLs to the client if there are files to be
         // uploaded
-        if (urls.size() > 0) {
+        if (!urls.isEmpty()) {
             getRpcProxy(FileDropTargetClientRpc.class).sendUploadUrl(urls);
         }
     }

server/src/test/java/com/vaadin/tests/server/componentcontainer/AddRemoveComponentTest.java

 package com.vaadin.tests.server.componentcontainer;
 
 import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.assertFalse;
 
 import java.lang.reflect.Constructor;
 import java.lang.reflect.InvocationTargetException;
         List<Class<? extends ComponentContainer>> containerClasses = VaadinClasses
                 .getComponentContainersSupportingAddRemoveComponent();
 
-        assertTrue(containerClasses.size() > 0);
+        assertFalse(containerClasses.isEmpty());
 
         // No default constructor, special case
         containerClasses.remove(CustomLayout.class);

server/src/test/java/com/vaadin/ui/AbstractMultiSelectTest.java

     }
 
     private void verifyValueChangeEvents() {
-        if (oldValues.size() > 0) {
+        if (!oldValues.isEmpty()) {
             assertTrue(oldValues.get(0).isEmpty());
             assertEquals(values.size(), oldValues.size());
             for (int i = 0; i < oldValues.size() - 1; i++) {

server/src/test/java/com/vaadin/ui/AbstractSingleSelectTest.java

     }
 
     private void verifyValueChanges() {
-        if (oldSelections.size() > 0) {
+        if (!oldSelections.isEmpty()) {
             assertEquals(null, oldSelections.get(0));
             assertEquals(selectionChanges.size(), oldSelections.size());
             for (int i = 0; i < oldSelections.size() - 1; i++) {

testbench-api/src/main/java/com/vaadin/testbench/elements/MenuBarElement.java

     private WebElement getSelectedTopLevelItem() {
         List<WebElement> selectedItems = findElements(
                 By.className("v-menubar-menuitem-selected"));
-        if (selectedItems.size() == 0) {
+        if (selectedItems.isEmpty()) {
             return null;
         }
         return selectedItems.get(0);

testbench-api/src/main/java/com/vaadin/testbench/elements/TabSheetElement.java

 
     // a locator that does not lead to selecting tabs from a contained inner
     // TabSheet (#13735)
-    protected org.openqa.selenium.By byTabCell = By
-            .xpath("./div/table/tbody/tr/td[contains(normalize-space(concat(' ', @class, ' ')),"
+    protected org.openqa.selenium.By byTabCell = By.xpath(
+            "./div/table/tbody/tr/td[contains(normalize-space(concat(' ', @class, ' ')),"
                     + "normalize-space(' v-tabsheet-tabitem '))]");
     private static org.openqa.selenium.By byCaption = By
             .className("v-captiontext");
     private void openTab(WebElement tabCell) {
         // Open the tab by clicking its caption text if it exists.
         List<WebElement> tabCaptions = tabCell.findElements(byCaption);
-        if (tabCaptions.size() > 0) {
+        if (!tabCaptions.isEmpty()) {
             tabCaptions.get(0).click();
             return;
         }
         // If no caption text was found, click the icon of the tab.
         List<WebElement> tabIcons = tabCell
                 .findElements(By.className("v-icon"));
-        if (tabIcons.size() > 0) {
+        if (!tabIcons.isEmpty()) {
             tabIcons.get(0).click();
             return;
         }
      */
     private String getTabCaption(WebElement tabCell) {
         List<WebElement> captionElements = tabCell.findElements(byCaption);
-        if (captionElements.size() == 0) {
+        if (captionElements.isEmpty()) {
             return null;
         } else {
             return captionElements.get(0).getText();

testbench-api/src/main/java/com/vaadin/testbench/elements/TreeTableRowElement.java

     public void toggleExpanded() {
         List<WebElement> expandButtons = getWrappedElement()
                 .findElements(By.className("v-treetable-treespacer"));
-        if (expandButtons.size() > 0) {
+        if (!expandButtons.isEmpty()) {
             expandButtons.get(0).click();
         }
     }

testbench-api/src/main/java/com/vaadin/testbench/elements/TwinColSelectElement.java

             }
             deselButton.click();
         }
-        while (selectedOptions.getOptions().size() > 0) {
+        while (!selectedOptions.getOptions().isEmpty()) {
             selectedOptions.selectByIndex(0);
             deselButton.click();
         }

uitest/src/main/java/com/vaadin/tests/components/table/KeyControl.java

             public void valueChange(ValueChangeEvent event) {
                 @SuppressWarnings("unchecked")
                 Set<String> value = (Set<String>) table3.getValue();
-                selected3.setValue(value.size() == 0 ? "No selected items"
+                selected3.setValue(value.isEmpty() ? "No selected items"
                         : value + ": Total " + value.size() + " items");
             }
         });

uitest/src/main/java/com/vaadin/tests/components/table/LargeSelectionCausesNPE.java

                 // in multiselect mode, a Set of itemIds is returned,
                 // in singleselect mode the itemId is returned directly
                 Set<?> value = (Set<?>) event.getProperty().getValue();
-                if (null == value || value.size() == 0) {
+                if (null == value || value.isEmpty()) {
                     selected.setValue("No selection");
                 } else {
                     selected.setValue("Selected: " + table.getValue());

uitest/src/main/java/com/vaadin/v7/tests/components/tree/CtrlShiftMultiselect.java

                     @SuppressWarnings("unchecked")
                     // safe cast after instanceof check
                     Set<Object> itemIds = (Set<Object>) tree.getValue();
-                    if (itemIds.size() == 0) {
+                    if (itemIds.isEmpty()) {
                         valueLbl.setValue("No selection");
                     } else {
                         valueLbl.setValue(itemIds.toString());

uitest/src/main/java/com/vaadin/v7/tests/components/tree/ExpandCollapseTree.java

                     @SuppressWarnings("unchecked")
                     // safe cast after instanceof check
                     Set<Object> itemIds = (Set<Object>) tree.getValue();
-                    if (itemIds.size() == 0) {
+                    if (itemIds.isEmpty()) {
                         valueLbl.setValue("No selection");
                     } else {
                         valueLbl.setValue(itemIds.toString());

uitest/src/test/java/com/vaadin/tests/components/HasValueRequiredIndicatorTest.java

  */
 package com.vaadin.tests.components;
 
+import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 
 import java.util.List;
     public void requiredIndicatorVisible() {
         openTestURL();
         List<WebElement> layouts = findElements(By.className("vaadin-layout"));
-        assertTrue(layouts.size() > 0);
+        assertFalse(layouts.isEmpty());
         layouts.stream().forEach(this::checkRequiredIndicator);
     }
 

uitest/src/test/java/com/vaadin/tests/components/checkboxgroup/CheckBoxGroupTest.java

 import java.util.List;
 import java.util.stream.Collectors;
 
-import org.junit.Assert;
 import org.junit.Before;
 import org.junit.Test;
 import org.openqa.selenium.By;
         assertItemSuffices(20);
         List<WebElement> icons = getSelect()
                 .findElements(By.cssSelector(".v-select-optiongroup .v-icon"));
-        assertTrue(icons.size() > 0);
+        assertFalse(icons.isEmpty());
         for (int i = 0; i < icons.size(); i++) {
             assertEquals(VaadinIcons.values()[i + 1].getCodepoint(),
                     icons.get(i).getText().charAt(0));
     }
 
     private void assertSelected(String... expectedSelection) {
-        assertEquals(Arrays.asList(expectedSelection),
-                getSelect().getValue());
+        assertEquals(Arrays.asList(expectedSelection), getSelect().getValue());
     }
 
     @Override
         List<String> optionsIcons = new ArrayList<>();
         for (WebElement option : getSelect().getOptionElements()) {
             List<WebElement> images = option.findElements(By.tagName("img"));
-            if (images.size() > 0) {
+            if (!images.isEmpty()) {
                 optionsIcons.add(images.get(0).getAttribute("src"));
             } else {
                 optionsIcons.add(null);

uitest/src/test/java/com/vaadin/tests/components/grid/GridHeaderFooterComponentsTest.java

             int col) {
         GridCellElement cell = grid.getHeaderCell(row, col);
         List<TextFieldElement> all = cell.$(TextFieldElement.class).all();
-        if (all.size() == 0) {
+        if (all.isEmpty()) {
             return null;
         } else if (all.size() == 1) {
             return all.get(0);
             int col) {
         GridCellElement cell = grid.getFooterCell(row, col);
         List<TextFieldElement> all = cell.$(TextFieldElement.class).all();
-        if (all.size() == 0) {
+        if (all.isEmpty()) {
             return null;
         } else if (all.size() == 1) {
             return all.get(0);

uitest/src/test/java/com/vaadin/tests/components/table/TableInIframeRowClickScrollJumpTest.java

 package com.vaadin.tests.components.table;
 
 import static org.hamcrest.MatcherAssert.assertThat;
+import static org.junit.Assert.assertFalse;
 
 import java.util.List;
 
 import org.openqa.selenium.WebElement;
 
 import com.vaadin.testbench.By;
-import com.vaadin.testbench.elements.TableElement;
 import com.vaadin.testbench.elements.ButtonElement;
+import com.vaadin.testbench.elements.TableElement;
 import com.vaadin.tests.tb3.MultiBrowserTest;
 
 /**
 
     public void switchIntoIframe() {
         List<WebElement> frames = driver.findElements(By.tagName("iframe"));
-        assertThat("No frames was found", frames.size() > 0);
+        assertFalse("No frames was found", frames.isEmpty());
         driver.switchTo().frame(frames.get(0));
     }
 

uitest/src/test/java/com/vaadin/tests/components/table/TableToggleColumnVisibilityTest.java

 package com.vaadin.tests.components.table;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 
 import org.junit.Test;
         assertTrue("Column header text should be custom",
                 headerCell.getText().equalsIgnoreCase("Hello World"));
 
-        assertTrue("Column should have an icon",
-                headerCell.findElements(By.className("v-icon")).size() > 0);
+        assertFalse("Column should have an icon",
+                headerCell.findElements(By.className("v-icon")).isEmpty());
 
-        assertTrue("Column should have alignment to the right", headerCell
+        assertFalse("Column should have alignment to the right", headerCell
                 .findElements(
                         By.className("v-table-caption-container-align-right"))
-                .size() > 0);
+                .isEmpty());
     }
 }

uitest/src/test/java/com/vaadin/tests/elements/tabsheet/TabSheetElementTabWithoutCaptionTest.java

         List<WebElement> openTabCaptionElements = tab
                 .findElement(By.className("v-caption"))
                 .findElements(By.className("v-captiontext"));
-        if (openTabCaptionElements.size() > 0) {
+        if (!openTabCaptionElements.isEmpty()) {
             String openTabCaption = openTabCaptionElements.get(0).getText();
             assertEquals("Wrong tab is open.", caption, openTabCaption);
         } else {
         boolean tabsOpen = false;
         for (int i = 0; i < tabs.size(); i++) {
             WebElement tab = tabs.get(i);
-            boolean isOpened = tab
+            boolean isOpened = !tab
                     .findElements(By.className("v-tabsheet-tabitem-selected"))
-                    .size() > 0;
+                    .isEmpty();
             if (isOpened) {
                 tabsOpen = true;
                 assertEquals("The wrong tab is open.", index, i);
                     + " should be open.");
         }
     }
-}
+}

uitest/src/test/java/com/vaadin/tests/smoke/CalendarSmokeTest.java

 
     private WebElement getFirstDayWithEvents() {
         for (WebElement monthDay : getCalendar().getMonthDays()) {
-            if (getVisibleEvents(monthDay).size() > 0) {
+            if (!getVisibleEvents(monthDay).isEmpty()) {
                 return monthDay;
             }
         }

uitest/src/test/java/com/vaadin/tests/tb3/AbstractTB3Test.java

             parameters.add("restartApplication");
         }
 
-        if (parameters.size() > 0) {
+        if (!parameters.isEmpty()) {
             url += "?" + StringUtils.join(parameters, "&");
         }