fix: tweak spotbugs errors

src/main/java/com/vlsolutions/swing/docking/DockTabbedPane.java

@@ -374,7 +374,7 @@ public void actionPerformed(ActionEvent e) {
 			//addTab(key.getName(), key.getIcon(), (Component)dc, key.getTooltip());
 			addTab("", smartIcon, (Component) dc, key.getTooltip());
 			//addTab(key.getName(),smartIcon, (Component) dc, key.getTooltip());
-			tab = getTabCount() - 1;
+			// tab = getTabCount() - 1;
 		} else {
 			//insertTab(key.getName(), key.getIcon(), (Component)dc, key.getTooltip(), tab);
 			insertTab("", smartIcon, (Component) dc, key.getTooltip(), tab);

src/main/java/com/vlsolutions/swing/docking/DockingContext.java

@@ -29,10 +29,8 @@
 
 import java.awt.Window;
 import java.awt.event.WindowEvent;
-import java.io.IOException;
-import java.io.InputStream;
-import java.io.OutputStream;
-import java.io.PrintWriter;
+import java.io.*;
+import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.Iterator;
@@ -243,16 +241,15 @@ public DockableState[] getDockables() {
 	 * @see #readXML(InputStream)
 	 * */
 	public void writeXML(OutputStream stream) throws IOException {
-		PrintWriter out = new PrintWriter(stream);
-		out.println("<?xml version=\"1.0\"?>");
-		out.println("<VLDocking version=\"2.1\">");
-		for(int i = 0; i < desktops.size(); i++) {
-			DockingDesktop desktop = (DockingDesktop) desktops.get(i);
-			desktop.writeDesktopNode(out);
+		try (PrintWriter out = new PrintWriter(new OutputStreamWriter(stream, StandardCharsets.UTF_8))) {
+			out.println("<?xml version=\"1.0\"?>");
+			out.println("<VLDocking version=\"2.1\">");
+            for (DockingDesktop dockingDesktop : desktops) {
+                dockingDesktop.writeDesktopNode(out);
+            }
+			out.println("</VLDocking>");
+			out.flush();
 		}
-		out.println("</VLDocking>");
-
-		out.flush();
 	}
 
 	/** Reads an XML encoded stream as the new desktop configuration.

src/main/java/com/vlsolutions/swing/docking/DockingDesktop.java

@@ -44,10 +44,7 @@
 import java.awt.event.WindowListener;
 import java.beans.PropertyChangeEvent;
 import java.beans.PropertyChangeListener;
-import java.io.IOException;
-import java.io.InputStream;
-import java.io.OutputStream;
-import java.io.PrintWriter;
+import java.io.*;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.Iterator;
@@ -1315,31 +1312,29 @@ private void splitTab(Component base, TabbedDockableContainer tdc,
 			DockingConstants.Split position) {
 		// should be used only when drag and dropping
 
-		if (base == null)
+		if (base == null) {
 			throw new NullPointerException("base");
-		Dockable firstDockable = tdc.getDockableAt(0);
-		DockableState currentState = getDockableState(firstDockable);
-		boolean stateChange = false;
-		if (currentState.isFloating()) {
-			removePreviousFloatingStates(tdc); // clear reference of the
-												// previous state
-			stateChange = true;
 		}
 
-		Container oldContainer = (Container) tdc;
-		int oldWidth = 0;
-		int oldHeight = 0;
-		if (oldContainer != null) {
+		int oldWidth;
+		int oldHeight;
+		boolean stateChange = false;
+		if (tdc instanceof Container) {
+			Container oldContainer = (Container) tdc;
 			oldWidth = oldContainer.getWidth();
 			oldHeight = oldContainer.getHeight();
+            DockableState currentState = getDockableState(tdc.getDockableAt(0));
+			if (currentState.isFloating()) {
+				removePreviousFloatingStates(tdc); // clear reference of the
+				// previous state
+				stateChange = true;
+			}
 		} else {
-			oldWidth = base.getWidth() / 2;
+            oldWidth = base.getWidth() / 2;
 			oldHeight = base.getHeight() / 2;
 		}
 
-		DockableContainer dockableContainer = tdc;
-
-		// create a new splitcontainer that will replace baseDockable's
+        // create a new splitcontainer that will replace baseDockable's
 		// container
 		SplitContainer split;
 		if (position == DockingConstants.SPLIT_TOP
@@ -1358,10 +1353,10 @@ private void splitTab(Component base, TabbedDockableContainer tdc,
 
 			if (position == DockingConstants.SPLIT_TOP
 					|| position == DockingConstants.SPLIT_LEFT) {
-				split.setLeftComponent((Component) dockableContainer);
+				split.setLeftComponent((Component) tdc);
 				split.setRightComponent(base);
 			} else {
-				split.setRightComponent((Component) dockableContainer);
+				split.setRightComponent((Component) tdc);
 				split.setLeftComponent(base);
 			}
 		} else {
@@ -1372,14 +1367,14 @@ private void splitTab(Component base, TabbedDockableContainer tdc,
 						split);
 				if (position == DockingConstants.SPLIT_TOP
 						|| position == DockingConstants.SPLIT_LEFT) {
-					split.setLeftComponent((Component) dockableContainer);
+					split.setLeftComponent((Component) tdc);
 					split.setRightComponent(dockingPanelChild);
 				} else {
-					split.setRightComponent((Component) dockableContainer);
+					split.setRightComponent((Component) tdc);
 					split.setLeftComponent(dockingPanelChild);
 				}
 			} else { // dockingpanel is empty
-				dockingPanel.add((Component) dockableContainer);
+				dockingPanel.add((Component) tdc);
 			}
 
 		}
@@ -1832,8 +1827,12 @@ public void restore(final Dockable dockable) {
 
 		DockableState currentState = getDockableState(dockable);
 		@SuppressWarnings("null")
-		boolean stateChange = currentState != null
-				|| currentState.isMaximized();
+		boolean stateChange;
+		if (currentState == null) {
+			stateChange = false;
+		} else {
+            stateChange = currentState.isMaximized();
+		}
 		DockableState newState = new DockableState(this, dockable,
 				DockableState.Location.DOCKED);
 		DockableState.Location currentLocation = getLocation(currentState);
@@ -3011,17 +3010,26 @@ void writeDesktopNode(PrintWriter out) throws IOException {
 
 		Window desktopWindow = SwingUtilities.getWindowAncestor(this);
 		Point windowLocation;
-		if (desktopWindow != null) {
-			windowLocation = desktopWindow.getLocation();
-		} else {
-			windowLocation = new Point(); // fail safe
-		}
-
-		out.println("<DockingDesktop name=\"" + desktopName + "\">");
-		out.println("<DockingPanel x=\"" + (int) windowLocation.getX()
-				+ "\" y=\"" + (int) windowLocation.getY() + "\" width=\""
-				+ desktopWindow.getWidth() + "\" height=\""
-				+ desktopWindow.getHeight() + "\"" + ">");
+		long x;
+		long y;
+		int width;
+		int height;
+        if (desktopWindow == null) {
+			x = 0;
+			y = 0;
+			width = 0;
+			height = 0;
+        } else {
+            windowLocation = desktopWindow.getLocation();
+			x = Math.round(windowLocation.getX());
+			y = Math.round(windowLocation.getY());
+			width = desktopWindow.getWidth();
+			height = desktopWindow.getHeight();
+        }
+
+        out.println("<DockingDesktop name=\"" + desktopName + "\">");
+		out.println("<DockingPanel x=\"" + x + "\" y=\"" + y
+				+ "\" width=\"" + width + "\" height=\"" + height + "\"" + ">");
 		if (dockingPanel.getComponentCount() > 0) {
 			// only one top component (DockableContainer or SplitContainer)
 			xmlWriteComponent(dockingPanel.getComponent(0), out);
@@ -3037,9 +3045,9 @@ void writeDesktopNode(PrintWriter out) throws IOException {
 
 		out.println("</DockingPanel>");
 
-		for (int i = 0; i < borderPanes.length; i++) {
-			xmlWriteBorder(borderPanes[i], out);
-		}
+        for (AutoHideButtonPanel borderPane : borderPanes) {
+            xmlWriteBorder(borderPane, out);
+        }
 
 		// finish with the floating dockables
 		xmlWriteFloating(out);
@@ -3072,11 +3080,12 @@ private void xmlWriteFloating(PrintWriter out) throws IOException {
 
 		Window desktopWindow = SwingUtilities.getWindowAncestor(this);
 		Point windowLocation;
+		/*
 		if (desktopWindow != null) {
 			windowLocation = desktopWindow.getLocation();
 		} else {
 			windowLocation = new Point(); // fail safe
-		}
+		}*/
 
 		ArrayList<Dockable> floatingDockables = context.getDockablesByState(
 				this, DockableState.Location.FLOATING);

src/main/java/com/vlsolutions/swing/docking/ui/AutoHideButtonPanelUI.java

@@ -49,7 +49,7 @@
  */
 public class AutoHideButtonPanelUI extends BasicPanelUI implements PropertyChangeListener {
 
-	private static AutoHideButtonPanelUI instance = new AutoHideButtonPanelUI();
+	private static final AutoHideButtonPanelUI instance = new AutoHideButtonPanelUI();
 
 	public static ComponentUI createUI(JComponent c) {
 		return instance;

src/main/java/com/vlsolutions/swing/docking/ui/AutoHideButtonUI.java

@@ -53,7 +53,7 @@
  */
 public class AutoHideButtonUI extends BasicLabelUI implements PropertyChangeListener {
 
-	protected static AutoHideButtonUI instance = new AutoHideButtonUI();
+	protected static final AutoHideButtonUI instance = new AutoHideButtonUI();
 
 	public AutoHideButtonUI() {}
 

src/main/java/com/vlsolutions/swing/docking/ui/DockingUISettings.java

@@ -752,7 +752,7 @@ public void installDockViewTitleBarSettings() {
 		UIManager.put("DockViewTitleBarUI",
 				"com.vlsolutions.swing.docking.ui.DockViewTitleBarUI");
 
-		UIManager.put("DockViewTitleBar.height", new Integer(20));
+		UIManager.put("DockViewTitleBar.height", 20);
 		UIManager.put("DockViewTitleBar.closeButtonText",
 				UIManager.getString("InternalFrameTitlePane.closeButtonText"));
 		UIManager.put("DockViewTitleBar.minimizeButtonText", UIManager
@@ -793,7 +793,7 @@ public void installDockViewTitleBarSettings() {
 	public void installSplitContainerSettings() {
 		UIManager.put("DockingSplitPaneUI",
 				"com.vlsolutions.swing.docking.ui.DockingSplitPaneUI");
-		UIManager.put("SplitContainer.dividerSize", new Integer(4));
+		UIManager.put("SplitContainer.dividerSize", 4);
 		UIManager.put("SplitContainer.isResizingEnabled", Boolean.TRUE); // 2007/08/11
 
 	}
@@ -802,8 +802,7 @@ public void installSplitContainerSettings() {
 	public void installTabbedContainerSettings() {
 		@SuppressWarnings("unused")
 		final String prefix = "/com/vldocking/swing/docking/";
-		UIManager.put("TabbedDockableContainer.tabPlacement", new Integer(
-				SwingConstants.TOP));
+		UIManager.put("TabbedDockableContainer.tabPlacement", SwingConstants.TOP);
 
 		UIManager.put("DockTabbedPane.closeButtonText",
 				UIManager.getString("InternalFrameTitlePane.closeButtonText"));
@@ -832,8 +831,8 @@ public void installTabbedContainerSettings() {
 	public void installCloseableTabs() {
 		// this one is already provided by the look and feel
 		// UIManager.put("TabbedPane.textIconGap", new Integer(4));
-		UIManager.put("TabbedPane.otherIconsGap", new Integer(8));
-		UIManager.put("TabbedPane.inBetweenOtherIconsGap", new Integer(4));
+		UIManager.put("TabbedPane.otherIconsGap", 8);
+		UIManager.put("TabbedPane.inBetweenOtherIconsGap", 4);
 		UIManager.put("TabbedPane.alternateTabIcons", Boolean.FALSE);
 	}
 
@@ -887,6 +886,9 @@ public void installIcons() {
 		UIManager.put("DockViewTitleBar.close", closeIcon);
 		UIManager.put("DockViewTitleBar.close.rollover", closeRolloverIcon);
 		UIManager.put("DockViewTitleBar.close.pressed", closePressedIcon);
+        UIManager.put("DockViewTitleBar.closeTab", closeTabIcon);
+        UIManager.put("DockViewTitleBar.closeTab.rollover", closeTabRolloverIcon);
+        UIManager.put("DockViewTitleBar.closeTab.pressed", closeTabPressedIcon);
 
 		UIManager.put("DockViewTitleBar.dock", new ImageIcon(getClass()
 				.getResource(prefix + "dock16v2.png")));
@@ -952,7 +954,7 @@ public void installIcons() {
 	public void installAccelerators() {
 
 		int MENU_SHORTCUT_MASK = Toolkit.getDefaultToolkit()
-				.getMenuShortcutKeyMask();
+				.getMenuShortcutKeyMaskEx();
 		// this returns CTRL_MASK or META_MASK depending on the platform
 		// (win/mac os)
 
@@ -961,7 +963,7 @@ public void installAccelerators() {
 		// toggle maximize/restore
 		UIManager
 				.put("DockingDesktop.maximizeActionAccelerator", KeyStroke
-						.getKeyStroke(KeyEvent.VK_ESCAPE, KeyEvent.SHIFT_MASK));
+						.getKeyStroke(KeyEvent.VK_ESCAPE, KeyEvent.SHIFT_DOWN_MASK));
 
 		// toggle autohide/dock
 		UIManager.put("DockingDesktop.dockActionAccelerator", KeyStroke
@@ -975,7 +977,7 @@ public void installAccelerators() {
 	/** installs the DockinDesktop related properties */
 	public void installDesktopSettings() {
 		UIManager.put("DockingDesktop.notificationColor", Color.ORANGE);
-		UIManager.put("DockingDesktop.notificationBlinkCount", new Integer(5));
+		UIManager.put("DockingDesktop.notificationBlinkCount", 5);
 		UIManager.put(
 				"DragControler.stopDragCursor",
 				new ImageIcon(getClass().getResource(