Bug 21631 JavaUI.createTypeDialog() should provide default message [dialogs]
2.0 Release If you use JavaUI.createTypeDialog() to create a new (single selection) type dialog, and then open the dialog, the open will fail silently. The dialog cannot be succesfully opened unless you send setMessage() to the dialog before you open it. This behaviour should be documented, or, preferably, a default message ("Please select a type/class/interface") should be provided.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/ui/JavaUI.java
* any character and '*' representing any string are supported. Clients can pass an empty 
	 * string if no filtering is required.
	 * @return a new selection dialog
	 * 
	 * @since 2.0
	 */
	public static SelectionDialog createMainTypeDialog(Shell parent, IRunnableContext context, IJavaSearchScope scope, int style, boolean multipleSelection, String filter) {
		if (multipleSelection) {
			MultiMainTypeSelectionDialog dialog= new MultiMainTypeSelectionDialog(parent, context, scope, style);
			dialog.setFilter(filter);
			return dialog;
		} else {
			MainTypeSelectionDialog dialog= new MainTypeSelectionDialog(parent, context, scope, style);
			dialog.setFilter(filter);
			return dialog;
		}		
	}
	/**
	 * Creates a selection dialog that lists all types in the given scope containing 
	 * a standard <code>main</code> method.
	 * The caller is responsible for opening the dialog with <code>Window.open</code>,
	 * and subsequently extracting the selected type(s) (of type
	 * <code>IType</code>) via <code>SelectionDialog.getResult</code>.
	 * 
	 * @param parent the parent shell of the dialog to be created
	 * @param context the runnable context used to show progress when the dialog
	 *   is being populated
	 * @param scope the scope that limits which types are included
	 * @param style flags defining the style of the dialog; the only valid values are
	 *   <code>IJavaElementSearchConstants.CONSIDER_BINARIES</code>,