UserInterface: push default behavior to interface

There is quite a bit of reasonable default behavior which can now,
thanks to Java 8, be expressed in default interface methods.

Author: ctrueden

src/main/java/org/scijava/ui/AbstractUserInterface.java

@@ -31,7 +31,6 @@
 
 package org.scijava.ui;
 
-import java.io.File;
 import java.util.List;
 
 import org.scijava.app.StatusService;
@@ -45,10 +44,8 @@
 import org.scijava.plugin.PluginService;
 import org.scijava.prefs.PrefService;
 import org.scijava.thread.ThreadService;
-import org.scijava.ui.console.ConsolePane;
 import org.scijava.ui.viewer.DisplayViewer;
 import org.scijava.ui.viewer.DisplayWindow;
-import org.scijava.widget.FileWidget;
 
 /**
  * Abstract superclass for {@link UserInterface} implementations.
@@ -102,11 +99,6 @@ public boolean isVisible() {
 		return visible;
 	}
 
-	@Override
-	public void show(final Object o) {
-		show(null, o);
-	}
-
 	@Override
 	public void show(final String name, final Object o) {
 		final Display<?> display;
@@ -163,44 +155,6 @@ public void run() {
 		});
 	}
 
-	@Override
-	public Desktop getDesktop() {
-		return null;
-	}
-
-	@Override
-	public ApplicationFrame getApplicationFrame() {
-		return null;
-	}
-
-	@Override
-	public ToolBar getToolBar() {
-		return null;
-	}
-
-	@Override
-	public StatusBar getStatusBar() {
-		return null;
-	}
-
-	@Override
-	public ConsolePane<?> getConsolePane() {
-		return null;
-	}
-
-	@Override
-	public File chooseFile(final File file, final String style) {
-		return chooseFile(fileChooserTitle(style), file, style);
-	}
-
-	@Deprecated
-	@Override
-	public File chooseFile(final String title, final File file,
-		final String style)
-	{
-		throw new UnsupportedOperationException("No default implementation.");
-	}
-
 	@Override
 	public void saveLocation() {
 		final ApplicationFrame appFrame = getApplicationFrame();
@@ -230,13 +184,4 @@ public void restoreLocation() {
 	protected void createUI() {
 		restoreLocation();
 	}
-
-	/** Gets a default file chooser title to use when none is given. */
-	protected String fileChooserTitle(final String style) {
-		if (style.equals(FileWidget.DIRECTORY_STYLE)) return "Choose a directory";
-		if (style.equals(FileWidget.OPEN_STYLE)) return "Open";
-		if (style.equals(FileWidget.SAVE_STYLE)) return "Save";
-		return "Choose a file";
-	}
-
 }

src/main/java/org/scijava/ui/UserInterface.java

@@ -70,7 +70,9 @@ public interface UserInterface extends RichPlugin, Disposable {
 	boolean isVisible();
 
 	/** Shows the object onscreen using an appropriate UI widget. */
-	void show(Object o);
+	default void show(final Object o) {
+		show(null, o);
+	}
 
 	/**
 	 * Shows the object onscreen using an appropriate UI widget.
@@ -87,25 +89,37 @@ public interface UserInterface extends RichPlugin, Disposable {
 	 * Gets the desktop, for use with multi-document interfaces (MDI), or null if
 	 * not applicable.
 	 */
-	Desktop getDesktop();
+	default Desktop getDesktop() {
+		return null;
+	}
 
 	/** Gets the main SciJava application frame, or null if not applicable. */
-	ApplicationFrame getApplicationFrame();
+	default ApplicationFrame getApplicationFrame() {
+		return null;
+	}
 
 	/** Gets the main SciJava toolbar, or null if not applicable. */
-	ToolBar getToolBar();
+	default ToolBar getToolBar() {
+		return null;
+	}
 
 	/** Gets the main SciJava status bar, or null if not applicable. */
-	StatusBar getStatusBar();
+	default StatusBar getStatusBar() {
+		return null;
+	}
 
 	/** Gets the main SciJava console pane, or null if not applicable. */
-	ConsolePane<?> getConsolePane();
+	default ConsolePane<?> getConsolePane() {
+		return null;
+	}
 
 	/**
 	 * Gets the system clipboard associated with this UI, or null if not
 	 * applicable.
 	 */
-	SystemClipboard getSystemClipboard();
+	default SystemClipboard getSystemClipboard() {
+		return null;
+	}
 
 	/**
 	 * Creates a new display window housing the given display, or null if not
@@ -142,7 +156,15 @@ DialogPrompt dialogPrompt(String message, String title,
 	 * @return The {@link File} chosen by the user, or null if prompt is not
 	 *         available
 	 */
-	File chooseFile(File file, String style);
+	default File chooseFile(final File file, final String style) {
+		final String title;
+		if (style.equals(FileWidget.DIRECTORY_STYLE)) title = "Choose a directory";
+		else if (style.equals(FileWidget.OPEN_STYLE)) title = "Open";
+		else if (style.equals(FileWidget.SAVE_STYLE)) title = "Save";
+		else title = "Choose a file";
+
+		return chooseFile(title, file, style);
+	}
 
 	/**
 	 * Prompts the user to choose a file.
@@ -158,7 +180,9 @@ DialogPrompt dialogPrompt(String message, String title,
 	 * @return The {@link File} chosen by the user, or null if prompt is not
 	 *         available
 	 */
-	File chooseFile(String title, File file, String style);
+	default File chooseFile(String title, File file, String style) {
+		throw new UnsupportedOperationException();
+	}
 
 	/**
 	 * Displays a popup context menu for the given display at the specified