Code cleanup (#12333)

- removed unused private methods
- removed unused private variables
- removed unnecessary initializations
- removed unnecessary substring(0)
- removed inner assignments
- renamed private methods that started with upper case
- renamed static final variables to use upper case
- converted to use non-deprecated options
- suppressed unavoidable warnings
- divided long Strings to multiple lines
- added missing types
- added missing JavaDoc parameters
- formatting
- updated comments & JavaDocs

8 files changed, 118 insertions, 56 deletions

diff --git a/server/src/main/java/com/vaadin/ui/AbstractDateField.java b/server/src/main/java/com/vaadin/ui/AbstractDateField.java
index d194363b94..c22aff114d 100644
--- a/server/src/main/java/com/vaadin/ui/AbstractDateField.java
+++ b/server/src/main/java/com/vaadin/ui/AbstractDateField.java
@@ -427,7 +427,7 @@ public abstract class AbstractDateField<T extends Temporal & TemporalAdjuster &
     }
 
     /**
-     * Parses string representaion of date range limit into date type
+     * Parses string representation of date range limit into date type.
      *
      * @param temporalStr
      *            the string representation
@@ -1005,7 +1005,7 @@ public abstract class AbstractDateField<T extends Temporal & TemporalAdjuster &
                         .orElse(null));
     }
 
-    private Iterable<R> getResolutionsHigherOrEqualTo(R resoution) {
+    private Iterable<R> getResolutionsHigherOrEqualTo(R resolution) {
         return getResolutions().skip(resolution.ordinal())
                 .collect(Collectors.toList());
     }
@@ -1141,10 +1141,11 @@ public abstract class AbstractDateField<T extends Temporal & TemporalAdjuster &
     }
 
     /**
-     * Control whether value change event is emitted when user input value 
-     * does not meet the integrated range validator.
+     * Control whether value change event is emitted when user input value does
+     * not meet the integrated range validator.
      *
-     * @param preventInvalidInput Set to false to disable the value change event.
+     * @param preventInvalidInput
+     *            Set to false to disable the value change event.
      *
      * @since 8.13
      */
@@ -1153,8 +1154,8 @@ public abstract class AbstractDateField<T extends Temporal & TemporalAdjuster &
     }
 
     /**
-     * Check whether value change is emitted when user input value does
-     * not meet integrated range validator. The default is false.
+     * Check whether value change is emitted when user input value does not meet
+     * integrated range validator. The default is false.
      *
      * @return a Boolean value
      *
diff --git a/server/src/main/java/com/vaadin/ui/Grid.java b/server/src/main/java/com/vaadin/ui/Grid.java
index 7ffd333430..137f947401 100644
--- a/server/src/main/java/com/vaadin/ui/Grid.java
+++ b/server/src/main/java/com/vaadin/ui/Grid.java
@@ -275,7 +275,7 @@ public class Grid<T> extends AbstractListing<T> implements HasComponents,
          *            <code>true</code> if event is a result of user
          *            interaction, <code>false</code> if from API call
          */
-        public ColumnReorderEvent(Grid source, boolean userOriginated) {
+        public ColumnReorderEvent(Grid<?> source, boolean userOriginated) {
             super(source);
             this.userOriginated = userOriginated;
         }
@@ -306,6 +306,8 @@ public class Grid<T> extends AbstractListing<T> implements HasComponents,
          *
          * @param source
          *            the grid where the event originated from
+         * @param column
+         *            the column that was resized
          * @param userOriginated
          *            <code>true</code> if event is a result of user
          *            interaction, <code>false</code> if from API call
@@ -356,6 +358,16 @@ public class Grid<T> extends AbstractListing<T> implements HasComponents,
          * Creates a new {@code ItemClick} event containing the given item and
          * Column originating from the given Grid.
          *
+         * @param source
+         *            the grid where the event originated from
+         * @param column
+         *            the column that contains the clicked cell
+         * @param item
+         *            the item that was clicked
+         * @param mouseEventDetails
+         *            mouse event details about the click
+         * @param rowIndex
+         *            the index of the row that contains the clicked cell
          */
         public ItemClick(Grid<T> source, Column<T, ?> column, T item,
                 MouseEventDetails mouseEventDetails, int rowIndex) {
@@ -390,6 +402,7 @@ public class Grid<T> extends AbstractListing<T> implements HasComponents,
          * @return the grid
          */
         @Override
+        @SuppressWarnings("unchecked")
         public Grid<T> getSource() {
             return (Grid<T>) super.getSource();
         }
@@ -501,6 +514,7 @@ public class Grid<T> extends AbstractListing<T> implements HasComponents,
         }
 
         @Override
+        @SuppressWarnings("unchecked")
         public Grid<T> getComponent() {
             return (Grid<T>) super.getComponent();
         }
@@ -849,18 +863,18 @@ public class Grid<T> extends AbstractListing<T> implements HasComponents,
     public static class Column<T, V> extends AbstractExtension {
 
         /**
-         * behavior when parsing nested properties which may contain
-         * <code>null</code> values in the property chain
+         * Behavior when parsing nested properties which may contain
+         * <code>null</code> values in the property chain.
          */
         public enum NestedNullBehavior {
             /**
-             * throw a NullPointerException if there is a nested
-             * <code>null</code> value
+             * Throw a NullPointerException if there is a nested
+             * <code>null</code> value.
              */
             THROW,
             /**
-             * silently ignore any exceptions caused by nested <code>null</code>
-             * values
+             * Silently ignore any exceptions caused by nested <code>null</code>
+             * values.
              */
             ALLOW_NULLS
         }
@@ -1578,6 +1592,7 @@ public class Grid<T> extends AbstractListing<T> implements HasComponents,
          *            the expand ratio of this column. {@code 0} to not have it
          *            expand at all. A negative number to clear the expand
          *            value.
+         * @return this column
          * @throws IllegalStateException
          *             if the column is no longer attached to any grid
          * @see #setWidth(double)
@@ -1607,6 +1622,7 @@ public class Grid<T> extends AbstractListing<T> implements HasComponents,
          * <p>
          * Equal to calling {@link #setExpandRatio(int) setExpandRatio(-1)}
          *
+         * @return this column
          * @throws IllegalStateException
          *             if the column is no longer attached to any grid
          */
@@ -1790,6 +1806,7 @@ public class Grid<T> extends AbstractListing<T> implements HasComponents,
          *
          * @param pixels
          *            the maximum width
+         * @return this column
          * @throws IllegalStateException
          *             if the column is no longer attached to any grid
          * @see #setExpandRatio(int)
@@ -1826,6 +1843,7 @@ public class Grid<T> extends AbstractListing<T> implements HasComponents,
          * @param resizable
          *            {@code true} if this column should be resizable,
          *            {@code false} otherwise
+         * @return this column
          * @throws IllegalStateException
          *             if the column is no longer attached to any grid
          */
@@ -1961,8 +1979,8 @@ public class Grid<T> extends AbstractListing<T> implements HasComponents,
          *            {@code true} if column is editable; {@code false} if not
          * @return this column
          * @throws IllegalStateException
-         *            if editable is true and column has no editor binding or
-         *            component defined
+         *             if editable is true and column has no editor binding or
+         *             component defined
          *
          * @see #setEditorComponent(HasValue, Setter)
          * @see #setEditorBinding(Binding)
@@ -2045,6 +2063,9 @@ public class Grid<T> extends AbstractListing<T> implements HasComponents,
          * <strong>Note:</strong> The same component cannot be used for multiple
          * columns.
          *
+         * @param <C>
+         *            a class that extends both {@link HasValue} and
+         *            {@link Component}
          * @param editorComponent
          *            the editor component
          * @param setter
@@ -2081,6 +2102,11 @@ public class Grid<T> extends AbstractListing<T> implements HasComponents,
          * <strong>Note:</strong> The same component cannot be used for multiple
          * columns.
          *
+         * @param <F>
+         *            a value type
+         * @param <C>
+         *            a class that extends both {@link HasValue} (for type
+         *            {@code <F>}) and {@link Component}
          * @param editorComponent
          *            the editor component
          * @return this column
@@ -2113,8 +2139,8 @@ public class Grid<T> extends AbstractListing<T> implements HasComponents,
          * all currently available row data to be recreated and sent to the
          * client.
          *
-         * Note: Setting a new renderer will reset presentation provider if
-         * it exists.
+         * Note: Setting a new renderer will reset presentation provider if it
+         * exists.
          *
          * @param renderer
          *            the new renderer
@@ -2660,6 +2686,8 @@ public class Grid<T> extends AbstractListing<T> implements HasComponents,
      * @see Grid#Grid()
      * @see Grid#Grid(Class)
      *
+     * @param <BEAN>
+     *            the grid bean type
      * @param propertySet
      *            the property set implementation to use, not <code>null</code>.
      * @return a new grid using the provided property set, not <code>null</code>
@@ -2875,6 +2903,8 @@ public class Grid<T> extends AbstractListing<T> implements HasComponents,
      *
      * @param valueProvider
      *            the value provider
+     * @param <V>
+     *            the column value type
      *
      * @return the new column
      */
@@ -3061,8 +3091,8 @@ public class Grid<T> extends AbstractListing<T> implements HasComponents,
     /**
      * Removes the given column from this {@link Grid}.
      *
-     * Note: If you have Editor with binding in this Grid to this property, you need to remove that
-     * using removeBinding method provided by Binder.
+     * Note: If you have Editor with binding in this Grid to this property, you
+     * need to remove that using removeBinding method provided by Binder.
      *
      * @param column
      *            the column to remove
@@ -4014,6 +4044,7 @@ public class Grid<T> extends AbstractListing<T> implements HasComponents,
      *
      * @see Column#setId(String)
      */
+    @SuppressWarnings("unchecked")
     public void setColumns(String... columnIds) {
         // Must extract to an explicitly typed variable because otherwise javac
         // cannot determine which overload of setColumnOrder to use
@@ -4068,6 +4099,7 @@ public class Grid<T> extends AbstractListing<T> implements HasComponents,
      * @param columns
      *            the columns in the order they should be
      */
+    @SuppressWarnings("unchecked")
     public void setColumnOrder(Column<T, ?>... columns) {
         setColumnOrder(Stream.of(columns));
     }
@@ -4133,6 +4165,11 @@ public class Grid<T> extends AbstractListing<T> implements HasComponents,
         return new GridSingleSelect<>(this);
     }
 
+    /**
+     * Returns the {@link Editor} for this grid.
+     *
+     * @return the editor, not null
+     */
     public Editor<T> getEditor() {
         return editor;
     }
@@ -4223,6 +4260,7 @@ public class Grid<T> extends AbstractListing<T> implements HasComponents,
      *
      * @see #getSelectionModel()
      * @see GridSelectionModel
+     * @return the items in the current selection, not null
      */
     public Set<T> getSelectedItems() {
         return getSelectionModel().getSelectedItems();
@@ -4234,6 +4272,8 @@ public class Grid<T> extends AbstractListing<T> implements HasComponents,
      *
      * @see #getSelectionModel()
      * @see GridSelectionModel
+     * @param item
+     *            the item to select, not null
      */
     public void select(T item) {
         getSelectionModel().select(item);
@@ -4245,6 +4285,8 @@ public class Grid<T> extends AbstractListing<T> implements HasComponents,
      *
      * @see #getSelectionModel()
      * @see GridSelectionModel
+     * @param item
+     *            the item to deselect, not null
      */
     public void deselect(T item) {
         getSelectionModel().deselect(item);
@@ -4849,10 +4891,10 @@ public class Grid<T> extends AbstractListing<T> implements HasComponents,
      */
     protected void writeData(Element body, DesignContext designContext) {
         getDataProvider().fetch(new Query<>())
-                .forEach(item -> writeRow(body, item, designContext));
+                .forEach(item -> writeRow(body, item));
     }
 
-    private void writeRow(Element container, T item, DesignContext context) {
+    private void writeRow(Element container, T item) {
         Element tableRow = container.appendElement("tr");
         tableRow.attr("item", serializeDeclarativeRepresentation(item));
         if (getSelectionModel().isSelected(item)) {
diff --git a/server/src/main/java/com/vaadin/ui/GridLayout.java b/server/src/main/java/com/vaadin/ui/GridLayout.java
index 42886fd650..a65a3717c0 100644
--- a/server/src/main/java/com/vaadin/ui/GridLayout.java
+++ b/server/src/main/java/com/vaadin/ui/GridLayout.java
@@ -641,6 +641,7 @@ public class GridLayout extends AbstractLayout
          * Constructs an <code>OverlapsException</code>.
          *
          * @param existingArea
+         *            the existing area that needs overlapping
          */
         public OverlapsException(Area existingArea) {
             this.existingArea = existingArea;
@@ -698,6 +699,7 @@ public class GridLayout extends AbstractLayout
          * detail message.
          *
          * @param areaOutOfBounds
+         *            the area that exceeds the bounds of the grid
          */
         public OutOfBoundsException(Area areaOutOfBounds) {
             super(String.format("%s, layout dimension: %sx%s", areaOutOfBounds,
@@ -837,6 +839,7 @@ public class GridLayout extends AbstractLayout
      * by GridLayout.
      *
      * @param cursorX
+     *            current cursor x-position
      */
     public void setCursorX(int cursorX) {
         this.cursorX = cursorX;
@@ -1058,7 +1061,9 @@ public class GridLayout extends AbstractLayout
      * @see #setWidth(float, Unit)
      *
      * @param columnIndex
+     *            The column index, starting from 0 for the leftmost row.
      * @param ratio
+     *            the expand ratio
      */
     public void setColumnExpandRatio(int columnIndex, float ratio) {
         columnExpandRatio.put(columnIndex, ratio);
@@ -1072,6 +1077,7 @@ public class GridLayout extends AbstractLayout
      * @see #setColumnExpandRatio(int, float)
      *
      * @param columnIndex
+     *            The column index, starting from 0 for the leftmost row.
      * @return the expand ratio, 0.0f by default
      */
     public float getColumnExpandRatio(int columnIndex) {
@@ -1103,6 +1109,7 @@ public class GridLayout extends AbstractLayout
      * @param rowIndex
      *            The row index, starting from 0 for the topmost row.
      * @param ratio
+     *            the expand ratio
      */
     public void setRowExpandRatio(int rowIndex, float ratio) {
         rowExpandRatio.put(rowIndex, ratio);
@@ -1195,6 +1202,7 @@ public class GridLayout extends AbstractLayout
      * MarginInfo )
      */
     @Override
+    @SuppressWarnings("deprecation")
     public void setMargin(MarginInfo marginInfo) {
         getState().marginsBitmask = marginInfo.getBitMask();
     }
@@ -1205,6 +1213,7 @@ public class GridLayout extends AbstractLayout
      * @see com.vaadin.ui.Layout.MarginHandler#getMargin()
      */
     @Override
+    @SuppressWarnings("deprecation")
     public MarginInfo getMargin() {
         return new MarginInfo(getState(false).marginsBitmask);
     }
@@ -1430,7 +1439,7 @@ public class GridLayout extends AbstractLayout
         }
 
         if (components.isEmpty()) {
-            writeEmptyColsAndRows(design, designContext);
+            writeEmptyColsAndRows(design);
             return;
         }
 
@@ -1566,10 +1575,8 @@ public class GridLayout extends AbstractLayout
      * components in the {@link GridLayout}
      *
      * @param design
-     * @param designContext
      */
-    private void writeEmptyColsAndRows(Element design,
-            DesignContext designContext) {
+    private void writeEmptyColsAndRows(Element design) {
         int rowCount = getState(false).rows;
         int colCount = getState(false).columns;
 
diff --git a/server/src/main/java/com/vaadin/ui/Panel.java b/server/src/main/java/com/vaadin/ui/Panel.java
index 750652653f..6c3df6e291 100644
--- a/server/src/main/java/com/vaadin/ui/Panel.java
+++ b/server/src/main/java/com/vaadin/ui/Panel.java
@@ -334,7 +334,7 @@ public class Panel extends AbstractSingleComponentContainer
     public void writeDesign(Element design, DesignContext designContext) {
         super.writeDesign(design, designContext);
         // handle tabindex
-        Panel def = designContext.getDefaultInstance(this);
+        designContext.getDefaultInstance(this);
     }
 
 }
diff --git a/server/src/main/java/com/vaadin/ui/TabSheet.java b/server/src/main/java/com/vaadin/ui/TabSheet.java
index 04c700e64e..64719e23a9 100644
--- a/server/src/main/java/com/vaadin/ui/TabSheet.java
+++ b/server/src/main/java/com/vaadin/ui/TabSheet.java
@@ -140,7 +140,7 @@ public class TabSheet extends AbstractComponentContainer
         registerRpc(new FocusAndBlurServerRpcDecorator(this, this::fireEvent));
 
         // expand horizontally by default
-        setWidth(100, UNITS_PERCENTAGE);
+        setWidth(100, Unit.PERCENTAGE);
         setCloseHandler(TabSheet::removeComponent);
     }
 
@@ -450,8 +450,7 @@ public class TabSheet extends AbstractComponentContainer
 
     @Override
     public void moveComponentsFrom(ComponentContainer source) {
-        for (final Iterator<Component> i = source.getComponentIterator(); i
-                .hasNext();) {
+        for (final Iterator<Component> i = source.iterator(); i.hasNext();) {
             final Component c = i.next();
             String caption = null;
             Resource icon = null;
@@ -644,8 +643,7 @@ public class TabSheet extends AbstractComponentContainer
      */
     private boolean updateSelection() {
         Component originalSelection = selected;
-        for (final Iterator<Component> i = getComponentIterator(); i
-                .hasNext();) {
+        for (final Iterator<Component> i = iterator(); i.hasNext();) {
             final Component component = i.next();
 
             Tab tab = tabs.get(component);
@@ -851,7 +849,8 @@ public class TabSheet extends AbstractComponentContainer
      * @since 3.0
      */
     @FunctionalInterface
-    public interface SelectedTabChangeListener extends SerializableEventListener {
+    public interface SelectedTabChangeListener
+            extends SerializableEventListener {
 
         /**
          * Selected (shown) tab in tab sheet has has been changed.
@@ -1015,11 +1014,15 @@ public class TabSheet extends AbstractComponentContainer
 
         /**
          * Gets the caption for the tab.
+         *
+         * @return the caption
          */
         public String getCaption();
 
         /**
          * Gets the icon for the tab.
+         *
+         * @return tue icon resource
          */
         public Resource getIcon();
 
@@ -1036,6 +1039,8 @@ public class TabSheet extends AbstractComponentContainer
          *
          * @param icon
          *            the icon to set
+         * @param iconAltText
+         *            the alt text
          */
         public void setIcon(Resource icon, String iconAltText);
 
@@ -1043,6 +1048,8 @@ public class TabSheet extends AbstractComponentContainer
          * Gets the icon alt text for the tab.
          *
          * @since 7.2
+         *
+         * @return the alt text
          */
         public String getIconAlternateText();
 
@@ -1114,11 +1121,15 @@ public class TabSheet extends AbstractComponentContainer
          * TODO currently not sent to the client
          *
          * @see AbstractComponent#setComponentError(ErrorMessage)
+         *
+         * @return the error message
          */
         public ErrorMessage getComponentError();
 
         /**
          * Get the component related to the Tab.
+         *
+         * @return the component
          */
         public Component getComponent();
 
@@ -1407,6 +1418,7 @@ public class TabSheet extends AbstractComponentContainer
      * The default CloseHandler for TabSheet will only remove the tab.
      *
      * @param handler
+     *            the close handler that should be used
      */
     public void setCloseHandler(CloseHandler handler) {
         closeHandler = handler;
@@ -1434,7 +1446,8 @@ public class TabSheet extends AbstractComponentContainer
      *
      * @param tab
      *            The tab
-     * @return
+     * @return the index of the given tab, or -1 if there is no such tab in this
+     *         tabsheet
      */
     public int getTabPosition(Tab tab) {
         return components.indexOf(tab.getComponent());
@@ -1659,7 +1672,7 @@ public class TabSheet extends AbstractComponentContainer
     public void writeDesign(Element design, DesignContext designContext) {
         super.writeDesign(design, designContext);
         TabSheet def = designContext.getDefaultInstance(this);
-        Attributes attr = design.attributes();
+        design.attributes();
 
         // write tabs
         if (!designContext.shouldWriteChildren(this, def)) {
diff --git a/server/src/main/java/com/vaadin/ui/components/colorpicker/ColorPickerPopup.java b/server/src/main/java/com/vaadin/ui/components/colorpicker/ColorPickerPopup.java
index 409c930e1b..29925126cb 100644
--- a/server/src/main/java/com/vaadin/ui/components/colorpicker/ColorPickerPopup.java
+++ b/server/src/main/java/com/vaadin/ui/components/colorpicker/ColorPickerPopup.java
@@ -15,7 +15,6 @@
  */
 package com.vaadin.ui.components.colorpicker;
 
-import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
@@ -28,19 +27,19 @@ import com.vaadin.data.HasValue;
 import com.vaadin.shared.Registration;
 import com.vaadin.shared.ui.MarginInfo;
 import com.vaadin.shared.ui.colorpicker.Color;
-import com.vaadin.ui.TabSheet;
-import com.vaadin.ui.Window;
-import com.vaadin.ui.VerticalLayout;
-import com.vaadin.ui.HorizontalLayout;
-import com.vaadin.ui.Component;
-import com.vaadin.ui.Slider;
-import com.vaadin.ui.Layout;
+import com.vaadin.ui.AbstractColorPicker.Coordinates2Color;
 import com.vaadin.ui.Alignment;
 import com.vaadin.ui.Button;
-import com.vaadin.ui.HasComponents;
-import com.vaadin.ui.AbstractColorPicker.Coordinates2Color;
 import com.vaadin.ui.Button.ClickEvent;
+import com.vaadin.ui.Component;
+import com.vaadin.ui.HasComponents;
+import com.vaadin.ui.HorizontalLayout;
+import com.vaadin.ui.Layout;
+import com.vaadin.ui.Slider;
 import com.vaadin.ui.Slider.ValueOutOfBoundsException;
+import com.vaadin.ui.TabSheet;
+import com.vaadin.ui.VerticalLayout;
+import com.vaadin.ui.Window;
 
 /**
  * A component that represents color selection popup within a color picker.
@@ -206,11 +205,6 @@ public class ColorPickerPopup extends Window implements HasValue<Color> {
         history.setWidth("97%");
         history.setHeight("22px");
 
-        // Create the default colors
-        List<Color> defaultColors = new ArrayList<>();
-        defaultColors.add(Color.BLACK);
-        defaultColors.add(Color.WHITE);
-
         // Create the history
         VerticalLayout innerContainer = new VerticalLayout();
         innerContainer.setWidth("100%");
@@ -503,6 +497,7 @@ public class ColorPickerPopup extends Window implements HasValue<Color> {
     }
 
     @Override
+    @SuppressWarnings("deprecation")
     public Registration addValueChangeListener(
             ValueChangeListener<Color> listener) {
         Objects.requireNonNull(listener, "listener cannot be null");
diff --git a/server/src/main/java/com/vaadin/ui/components/colorpicker/ColorPickerPreview.java b/server/src/main/java/com/vaadin/ui/components/colorpicker/ColorPickerPreview.java
index 8782a5aa39..d70cf60313 100644
--- a/server/src/main/java/com/vaadin/ui/components/colorpicker/ColorPickerPreview.java
+++ b/server/src/main/java/com/vaadin/ui/components/colorpicker/ColorPickerPreview.java
@@ -49,8 +49,6 @@ public class ColorPickerPreview extends CssLayout implements HasValue<Color> {
     /** The field. */
     private final TextField field;
 
-    /** The old value. */
-    private String oldValue;
     private Registration valueChangeListenerRegistration = null;
 
     private boolean readOnly;
@@ -96,8 +94,6 @@ public class ColorPickerPreview extends CssLayout implements HasValue<Color> {
         field.setValue(colorCSS);
         field.setComponentError(null);
 
-        oldValue = colorCSS;
-
         // Re-register listener
         valueChangeListenerRegistration = field
                 .addValueChangeListener(this::valueChange);
@@ -121,6 +117,7 @@ public class ColorPickerPreview extends CssLayout implements HasValue<Color> {
     }
 
     @Override
+    @SuppressWarnings("deprecation")
     public Registration addValueChangeListener(
             ValueChangeListener<Color> listener) {
         Objects.requireNonNull(listener, "listener cannot be null");
@@ -141,7 +138,6 @@ public class ColorPickerPreview extends CssLayout implements HasValue<Color> {
              */
             color = ColorUtil.stringToColor(value);
 
-            oldValue = value;
             fireEvent(new ValueChangeEvent<>(this, oldColor,
                     event.isUserOriginated()));
         } catch (NumberFormatException e) {
diff --git a/server/src/main/java/com/vaadin/ui/declarative/DesignContext.java b/server/src/main/java/com/vaadin/ui/declarative/DesignContext.java
index b8f355d4a2..29efe4f7b4 100644
--- a/server/src/main/java/com/vaadin/ui/declarative/DesignContext.java
+++ b/server/src/main/java/com/vaadin/ui/declarative/DesignContext.java
@@ -354,10 +354,14 @@ public class DesignContext implements Serializable {
      * Returns the default instance for the given class. The instance must not
      * be modified by the caller.
      *
+     * @param <T>
+     *            a component class
      * @param component
+     *            the component that determines the class
      * @return the default instance for the given class. The return value must
      *         not be modified by the caller
      */
+    @SuppressWarnings("unchecked")
     public <T> T getDefaultInstance(Component component) {
         // If the root is a @DesignRoot component, it can't use itself as a
         // reference or the written design will be empty
@@ -385,6 +389,9 @@ public class DesignContext implements Serializable {
     /**
      * Reads and stores the mappings from prefixes to package names from meta
      * tags located under <head> in the html document.
+     *
+     * @param doc
+     *            the document
      */
     protected void readPackageMappings(Document doc) {
         Element head = doc.head();
@@ -848,7 +855,8 @@ public class DesignContext implements Serializable {
             String value) {
         Map<String, String> map = customAttributes.get(component);
         if (map == null) {
-            customAttributes.put(component, map = new HashMap<>());
+            map = new HashMap<>();
+            customAttributes.put(component, map);
         }
         map.put(attribute, value);
     }