Add EmptyLineSeparator checkstyle rule

Author: geofjamg

Diff for: checkstyle.xml

@@ -27,6 +27,12 @@
         <module name="EmptyCatchBlock">
             <property name="exceptionVariableName" value="ignored"/>
         </module>
+        <module name="EmptyLineSeparator">
+            <property name="allowNoEmptyLineBetweenFields" value="true"/>
+            <property name="allowMultipleEmptyLines" value="false"/>
+            <property name="allowMultipleEmptyLinesInsideClassMembers" value="false"/>
+            <property name="tokens" value="IMPORT, CLASS_DEF, INTERFACE_DEF, STATIC_INIT, INSTANCE_INIT, METHOD_DEF, CTOR_DEF, VARIABLE_DEF"/>
+        </module>
         <module name="EmptyStatement"/>
         <module name="EqualsHashCode"/>
         <module name="FinalClass"/>

Diff for: gse-app/src/main/java/com/powsybl/gse/app/ProjectPane.java

@@ -91,7 +91,6 @@ public static class MyTab extends Tab {
 
         private final KeyCombination closeAllKeyCombination = new KeyCodeCombination(KeyCode.W, KeyCombination.CONTROL_DOWN, KeyCombination.SHIFT_DOWN);
 
-
         public MyTab(String text, ProjectFileViewer viewer) {
             super(text, viewer.getContent());
             this.viewer = viewer;

Diff for: gse-util/src/main/java/com/powsybl/gse/util/DragAndDropMove.java

@@ -9,9 +9,10 @@
 import javafx.scene.control.TreeItem;
 
 public class DragAndDropMove {
+
     private Object source;
-    private TreeItem sourceTreeItem;
 
+    private TreeItem sourceTreeItem;
 
     public Object getSource() {
         return source;

Diff for: gse-util/src/main/java/com/powsybl/gse/util/NodeChooser.java

@@ -49,7 +49,6 @@ public class NodeChooser<N, F extends N, D extends N, T extends N> extends GridP
     private Set<String> openedProjects = new HashSet<>();
     private SimpleBooleanProperty deleteMenuItemDisableProperty = new SimpleBooleanProperty(false);
 
-
     public interface TreeModel<N, F, D> {
         Collection<N> getChildren(D folder);
 
@@ -396,7 +395,6 @@ private void refresh(TreeItem<N> item) {
         }
     }
 
-
     private void onMouseClickedEvent(MouseEvent event) {
         TreeItem<N> item = tree.getSelectionModel().getSelectedItem();
         N node = item != null ? item.getValue() : null;

Diff for: gse-util/src/main/java/com/powsybl/gse/util/SearchBar.java

@@ -171,7 +171,6 @@ public SearchBar(Searchable textArea) {
         setMargin(searchField, new Insets(0, 0, 0, 5));
         setMargin(closeButton, new Insets(0, 5, 0, 0));
 
-
         searchField.textProperty().addListener((observable, oldValue, newValue) -> {
             if (newValue == null || "".equals(newValue)) {
                 matcher.reset();
@@ -193,7 +192,6 @@ public SearchBar(Searchable textArea) {
             }
         });
 
-
         matcher.nbMatchesProperty().addListener((observable, oldValue, newValue) -> {
             if (newValue.intValue() == 0) {
                 textArea.deselect();