Refine checkstyle rules

- Add (and apply) checkstyle rules for
  - correct spacing (especalliy // space-after-comment-marker)
  - } else if { (<-- in one line)
  - no two empty lines
  - @Deprecation JavaDoc
  - some coding practices
- Fix HTML syntax of JavaDoc comments
- Remove CSS class comment syntax in IconTheme class
- Remove deprecated method BibEntry#getCiteKey()

config/checkstyle/checkstyle.xml

@@ -4,6 +4,8 @@
         "http://www.checkstyle.org/dtds/configuration_1_3.dtd">
 
 <module name="Checker">
+    <property name="charset" value="UTF-8"/>
+
     <module name="Header">
         <property name="header" value=""/>
     </module>
@@ -21,6 +23,9 @@
         <property name="fileNamePattern" value="module\-info\.java$"/>
     </module>
 
+    <module name="FileTabCharacter"/>
+    <module name="NewlineAtEndOfFile"/>
+
     <module name="TreeWalker">
         <!-- Checks for Javadoc comments: https://checkstyle.org/config_javadoc.html -->
         <module name="InvalidJavadocPosition"/>
@@ -42,16 +47,27 @@
             <property name="sortStaticImportsAlphabetically" value="true"/>
         </module>
 
-        <!-- Checks for common coding problems: https://checkstyle.org/config_coding.html -->
-        <module name="DeclarationOrder"/>
-
         <!-- Checks for whitespace: https://checkstyle.org/config_whitespace.html -->
+
+        <module name="EmptyForInitializerPad"/>
         <module name="EmptyLineSeparator">
+            <!-- check all except variable declarations -->
             <property name="tokens"
-                      value="IMPORT, CLASS_DEF, INTERFACE_DEF, ENUM_DEF, STATIC_INIT, INSTANCE_INIT, METHOD_DEF"/>
+                      value="IMPORT, STATIC_IMPORT, CLASS_DEF, INTERFACE_DEF, ENUM_DEF, STATIC_INIT, INSTANCE_INIT, METHOD_DEF, CTOR_DEF"/>
             <property name="allowMultipleEmptyLines" value="false"/>
             <property name="allowMultipleEmptyLinesInsideClassMembers" value="false"/>
         </module>
+        <module name="GenericWhitespace"/>
+        <module name="MethodParamPad"/>
+        <module name="NoLineWrap"/>
+        <module name="NoWhitespaceAfter"/>
+        <module name="NoWhitespaceBefore"/>
+        <module name="ParenPad"/>
+        <module name="SeparatorWrap">
+            <property name="tokens" value="COMMA, SEMI, ELLIPSIS, ARRAY_DECLARATOR, RBRACK, METHOD_REF"/>
+        </module>
+        <module name="SingleSpaceSeparator"/>
+        <module name="WhitespaceAfter"/>
         <module name="WhitespaceAround">
             <!-- RCULRY causes issues if classes are nested within arrays, therefore not activated -->
             <property name="tokens"
@@ -70,5 +86,44 @@
 
         <!-- Checks for blocks: https://checkstyle.org/config_blocks.html -->
         <module name="NeedBraces"/>
+
+        <module name="EmptyBlock">
+            <property name="option" value="text"/>
+        </module>
+
+        <!-- Disallows empty catch blocks (not even having a comment): https://checkstyle.sourceforge.io/config_blocks.html#EmptyCatchBlock -->
+        <module name="EmptyCatchBlock"/>
+
+        <!--
+            following rule enforces that there are no one line statements such as
+
+              public String getTabName() { return Localization.lang("XMP metadata"); }
+
+            Since it is too much effort to reformat all code, it is currently not enabled -->
+        <!-- <module name="LeftCurly"/> -->
+
+        <module name="RightCurly"/>
+        <!-- coding - https://checkstyle.sourceforge.io/config_coding.html -->
+
+        <module name="AvoidDoubleBraceInitialization"/>
+
+        <module name="CovariantEquals"/>
+
+        <!-- Checks for common coding problems: https://checkstyle.org/config_coding.html -->
+
+        <module name="DeclarationOrder"/>
+        <module name="EmptyStatement"/>
+
+        <module name="EqualsHashCode"/>
+
+        <!-- force a space after // for comments -->
+        <module name="TodoComment">
+            <property name="id" value="commentStartWithSpace"/>
+            <property name="format" value="^([^\s\/*])"/>
+            <message key="todo.match" value="Comment text should start with space."/>
+        </module>
+
+        <module name="MissingDeprecated"/>
+
     </module>
 </module>

src/main/java/org/jabref/JabRefExecutorService.java

@@ -136,7 +136,7 @@ public void submit(TimerTask timerTask, long millisecondsDelay) {
     public void shutdownEverything() {
         // those threads will be allowed to finish
         this.executorService.shutdown();
-        //those threads will be interrupted in their current task
+        // those threads will be interrupted in their current task
         this.lowPriorityExecutorService.shutdownNow();
         // kill the remote thread
         stopRemoteThread();

src/main/java/org/jabref/JabRefGUI.java

@@ -65,7 +65,7 @@ private void openWindow(Stage mainStage) {
         if (Globals.prefs.getBoolean(JabRefPreferences.WINDOW_MAXIMISED)) {
             mainStage.setMaximized(true);
         } else if (Screen.getScreens().size() == 1 && isWindowPositionOutOfBounds()) {
-            //corrects the Window, if its outside of the mainscreen
+            // corrects the Window, if its outside of the mainscreen
             LOGGER.debug("The Jabref Window is outside the Main Monitor\n");
             mainStage.setX(0);
             mainStage.setY(0);
@@ -94,8 +94,8 @@ private void openWindow(Stage mainStage) {
 
         mainStage.setOnCloseRequest(event -> {
             if (!correctedWindowPos) {
-                //saves the window position only if its not  corrected -> the window will rest at the old Position,
-                //if the external Screen is connected again.
+                // saves the window position only if its not  corrected -> the window will rest at the old Position,
+                // if the external Screen is connected again.
                 saveWindowState(mainStage);
             }
             boolean reallyQuit = mainFrame.quit();

src/main/java/org/jabref/cli/ArgumentProcessor.java

@@ -241,8 +241,8 @@ private List<ParserResult> processArguments() {
 
     private boolean exportMatches(List<ParserResult> loaded) {
         String[] data = cli.getExportMatches().split(",");
-        String searchTerm = data[0].replace("\\$", " "); //enables blanks within the search term:
-        //$ stands for a blank
+        String searchTerm = data[0].replace("\\$", " "); // enables blanks within the search term:
+        // $ stands for a blank
         ParserResult pr = loaded.get(loaded.size() - 1);
         BibDatabaseContext databaseContext = pr.getDatabaseContext();
         BibDatabase dataBase = pr.getDatabase();
@@ -252,17 +252,17 @@ private boolean exportMatches(List<ParserResult> loaded) {
                 searchPreferences.isRegularExpression());
         List<BibEntry> matches = new DatabaseSearcher(query, dataBase).getMatches();
 
-        //export matches
+        // export matches
         if (!matches.isEmpty()) {
             String formatName;
 
-            //read in the export format, take default format if no format entered
+            // read in the export format, take default format if no format entered
             switch (data.length) {
                 case 3:
                     formatName = data[2];
                     break;
                 case 2:
-                    //default exporter: HTML table (with Abstract & BibTeX)
+                    // default exporter: HTML table (with Abstract & BibTeX)
                     formatName = "tablerefsabsbib";
                     break;
                 default:
@@ -272,7 +272,7 @@ private boolean exportMatches(List<ParserResult> loaded) {
                     return false;
             }
 
-            //export new database
+            // export new database
             Optional<Exporter> exporter = Globals.exportFactory.getExporterByName(formatName);
             if (!exporter.isPresent()) {
                 System.err.println(Localization.lang("Unknown export format") + ": " + formatName);

src/main/java/org/jabref/gui/AbstractViewModel.java

@@ -1,5 +1,5 @@
 package org.jabref.gui;
 
 public class AbstractViewModel {
-    //empty
+    // empty
 }

src/main/java/org/jabref/gui/EntryTypeView.java

@@ -69,7 +69,7 @@ public EntryTypeView(BasePanel basePanel, DialogService dialogService, JabRefPre
         ControlHelper.setAction(generateButton, this.getDialogPane(), event -> viewModel.runFetcherWorker());
 
         setResultConverter(button -> {
-            //The buttonType will always be cancel, even if we pressed one of the entry type buttons
+            // The buttonType will always be cancel, even if we pressed one of the entry type buttons
             return type;
         });
 
@@ -112,8 +112,8 @@ public void initialize() {
 
         new ViewModelListCellFactory<IdBasedFetcher>().withText(item -> item.getName()).install(idBasedFetchers);
 
-        //we set the managed property so that they will only be rendered when they are visble so that the Nodes only take the space when visible
-        //avoids removing and adding from the scence graph
+        // we set the managed property so that they will only be rendered when they are visble so that the Nodes only take the space when visible
+        // avoids removing and adding from the scence graph
         bibTexTitlePane.managedProperty().bind(bibTexTitlePane.visibleProperty());
         ieeeTranTitlePane.managedProperty().bind(ieeeTranTitlePane.visibleProperty());
         biblatexTitlePane.managedProperty().bind(biblatexTitlePane.visibleProperty());

src/main/java/org/jabref/gui/JabRefFrame.java

@@ -293,7 +293,7 @@ public void setWindowTitle() {
 
         // no database open
         if (panel == null) {
-            //setTitle(FRAME_TITLE);
+            // setTitle(FRAME_TITLE);
             return;
         }
 
@@ -307,9 +307,9 @@ public void setWindowTitle() {
                                        .getDatabasePath()
                                        .map(Path::toString)
                                        .orElse(Localization.lang("untitled"));
-            //setTitle(FRAME_TITLE + " - " + databaseFile + changeFlag + modeInfo);
+            // setTitle(FRAME_TITLE + " - " + databaseFile + changeFlag + modeInfo);
         } else if (panel.getBibDatabaseContext().getLocation() == DatabaseLocation.SHARED) {
-            //setTitle(FRAME_TITLE + " - " + panel.getBibDatabaseContext().getDBMSSynchronizer().getDBName() + " ["
+            // setTitle(FRAME_TITLE + " - " + panel.getBibDatabaseContext().getDBMSSynchronizer().getDBName() + " ["
             //        + Localization.lang("shared") + "]" + modeInfo);
         }
     }
@@ -343,7 +343,7 @@ public JabRefPreferences prefs() {
      *                  set to true
      */
     private void tearDownJabRef(List<String> filenames) {
-        //prefs.putBoolean(JabRefPreferences.WINDOW_MAXIMISED, getExtendedState() == Frame.MAXIMIZED_BOTH);
+        // prefs.putBoolean(JabRefPreferences.WINDOW_MAXIMISED, getExtendedState() == Frame.MAXIMIZED_BOTH);
 
         if (prefs.getBoolean(JabRefPreferences.OPEN_LAST_EDITED)) {
             // Here we store the names of all current files. If
@@ -554,10 +554,10 @@ public void init() {
 
         initDragAndDrop();
 
-        //setBounds(GraphicsEnvironment.getLocalGraphicsEnvironment().getMaximumWindowBounds());
-        //WindowLocation pw = new WindowLocation(this, JabRefPreferences.POS_X, JabRefPreferences.POS_Y, JabRefPreferences.SIZE_X,
+        // setBounds(GraphicsEnvironment.getLocalGraphicsEnvironment().getMaximumWindowBounds());
+        // WindowLocation pw = new WindowLocation(this, JabRefPreferences.POS_X, JabRefPreferences.POS_Y, JabRefPreferences.SIZE_X,
         //        JabRefPreferences.SIZE_Y);
-        //pw.displayWindowAtStoredLocation();
+        // pw.displayWindowAtStoredLocation();
 
         // Bind global state
         stateManager.activeDatabaseProperty().bind(
@@ -595,9 +595,9 @@ public void init() {
             stateManager.activeSearchQueryProperty().set(newBasePanel.getCurrentSearchQuery());
 
             // groupSidePane.getToggleCommand().setSelected(sidePaneManager.isComponentVisible(GroupSidePane.class));
-            //previewToggle.setSelected(Globals.prefs.getPreviewPreferences().isPreviewPanelEnabled());
-            //generalFetcher.getToggleCommand().setSelected(sidePaneManager.isComponentVisible(WebSearchPane.class));
-            //openOfficePanel.getToggleCommand().setSelected(sidePaneManager.isComponentVisible(OpenOfficeSidePanel.class));
+            // previewToggle.setSelected(Globals.prefs.getPreviewPreferences().isPreviewPanelEnabled());
+            // generalFetcher.getToggleCommand().setSelected(sidePaneManager.isComponentVisible(WebSearchPane.class));
+            // openOfficePanel.getToggleCommand().setSelected(sidePaneManager.isComponentVisible(OpenOfficeSidePanel.class));
 
             setWindowTitle();
             // Update search autocompleter with information for the correct database:
@@ -743,7 +743,7 @@ private MenuBar createMenu() {
             );
         }
 
-        //@formatter:off
+        // @formatter:off
         library.getItems().addAll(
                 factory.createMenuItem(StandardActions.NEW_ENTRY, new NewEntryAction(this, dialogService, Globals.prefs, stateManager)),
                 factory.createMenuItem(StandardActions.NEW_ENTRY_FROM_PLAIN_TEXT, new ExtractBibtexAction(stateManager)),
@@ -883,7 +883,7 @@ private MenuBar createMenu() {
                 factory.createMenuItem(StandardActions.ABOUT, new AboutAction())
         );
 
-        //@formatter:on
+        // @formatter:on
         MenuBar menu = new MenuBar();
         menu.getStyleClass().add("mainMenu");
         menu.getMenus().addAll(

src/main/java/org/jabref/gui/actions/JabRefAction.java

@@ -58,7 +58,7 @@ private String getActionName(Action action, Command command) {
             return action.getText();
         } else {
             String commandName = command.getClass().getSimpleName();
-            if ( commandName.contains("EditAction")
+            if (commandName.contains("EditAction")
                     || commandName.contains("CopyMoreAction")
                     || commandName.contains("CopyCitationAction")
                     || commandName.contains("PreviewSwitchAction")

src/main/java/org/jabref/gui/autocompleter/SuggestionProvider.java

@@ -149,9 +149,7 @@ public SuggestionProviderString(Callback<T, String> stringConverter) {
 
             // In case no stringConverter was provided, use the default strategy
             if (this.stringConverter == null) {
-                this.stringConverter = obj -> {
-                    return obj != null ? obj.toString() : ""; //$NON-NLS-1$
-                };
+                this.stringConverter = obj -> obj != null ? obj.toString() : "";
             }
         }
 

src/main/java/org/jabref/gui/bibtexextractor/ExtractBibtexDialog.java

@@ -52,7 +52,7 @@ public ExtractBibtexDialog() {
     @FXML
     private void initialize() {
         BibDatabaseContext database = stateManager.getActiveDatabase().orElseThrow(() -> new NullPointerException("Database null"));
-        this.viewModel = new BibtexExtractorViewModel(database, dialogService, JabRefPreferences.getInstance(), fileUpdateMonitor, taskExecutor,undoManager,stateManager);
+        this.viewModel = new BibtexExtractorViewModel(database, dialogService, JabRefPreferences.getInstance(), fileUpdateMonitor, taskExecutor, undoManager, stateManager);
         input.textProperty().bindBidirectional(viewModel.inputTextProperty());
     }
 }

src/main/java/org/jabref/gui/bibtexkeypattern/BibtexKeyPatternPanel.java

@@ -68,7 +68,7 @@ private void buildGUI() {
             Label keyPattern = new Label(Localization.lang("Key pattern"));
             gridPane.add(label, ++columnIndex, rowIndex);
             gridPane.add(keyPattern, ++columnIndex, rowIndex);
-            ++columnIndex; //3
+            columnIndex++;
         }
 
         rowIndex++;

src/main/java/org/jabref/gui/collab/ChangeDisplayDialog.java

@@ -79,19 +79,19 @@ public ChangeDisplayDialog(BibDatabaseContext database, List<DatabaseChangeViewM
         setResultConverter(button -> {
             if (button == dismissChanges) {
                 return false;
-
             } else {
                 // Perform all accepted changes
                 NamedCompound ce = new NamedCompound(Localization.lang("Merged external changes"));
                 for (DatabaseChangeViewModel change : changes) {
                     if (change instanceof EntryChangeViewModel) {
-                        change.makeChange(database, ce); //We don't have a checkbox for accept and always get the correct merged entry, the accept property in this special case only controls the radio buttons selection
+                        // We don't have a checkbox for accept and always get the correct merged entry, the accept property in this special case only controls the radio buttons selection
+                        change.makeChange(database, ce);
                     } else if (change.isAccepted()) {
                         change.makeChange(database, ce);
                     }
                 }
                 ce.end();
-                //TODO: panel.getUndoManager().addEdit(ce);
+                // TODO: panel.getUndoManager().addEdit(ce);
 
                 return true;
             }

src/main/java/org/jabref/gui/commonfxcontrols/BibtexKeyPatternPanel.java

@@ -80,13 +80,21 @@ private void initialize() {
         this.itemsProperty().bindBidirectional(viewModel.patternListProperty());
     }
 
-    public void setValues() { viewModel.setValues(); }
+    public void setValues() {
+        viewModel.setValues();
+    }
 
-    public void resetAll() { viewModel.resetAll(); }
+    public void resetAll() {
+        viewModel.resetAll();
+    }
 
-    public ListProperty<BibtexKeyPatternPanelItemModel> patternListProperty() { return viewModel.patternListProperty(); }
+    public ListProperty<BibtexKeyPatternPanelItemModel> patternListProperty() {
+        return viewModel.patternListProperty();
+    }
 
-    public ObjectProperty<BibtexKeyPatternPanelItemModel> defaultKeyPatternProperty() { return viewModel.defaultKeyPatternProperty(); }
+    public ObjectProperty<BibtexKeyPatternPanelItemModel> defaultKeyPatternProperty() {
+        return viewModel.defaultKeyPatternProperty();
+    }
 
     private void jumpToSearchKey(KeyEvent keypressed) {
         if (keypressed.getCharacter() == null) {

src/main/java/org/jabref/gui/commonfxcontrols/BibtexKeyPatternPanelItemModel.java

@@ -20,9 +20,13 @@ public BibtexKeyPatternPanelItemModel(EntryType entryType, String pattern) {
         this.pattern.setValue(pattern);
     }
 
-    public EntryType getEntryType() { return entryType.getValue(); }
+    public EntryType getEntryType() {
+        return entryType.getValue();
+    }
 
-    public ObjectProperty<EntryType> entryType() { return entryType; }
+    public ObjectProperty<EntryType> entryType() {
+        return entryType;
+    }
 
     public void setPattern(String pattern) {
         this.pattern.setValue(pattern);
@@ -32,8 +36,12 @@ public String getPattern() {
         return pattern.getValue();
     }
 
-    public StringProperty pattern() { return pattern; }
+    public StringProperty pattern() {
+        return pattern;
+    }
 
     @Override
-    public String toString() { return "[" + entryType.getValue().getName() + "," + pattern.getValue() + "]"; }
+    public String toString() {
+        return "[" + entryType.getValue().getName() + "," + pattern.getValue() + "]";
+    }
 }