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
* 
	 * @see org.eclipse.jdt.core.JavaCore#getSharedWorkingCopies(org.eclipse.jdt.core.IBufferFactory)
	 * @since 2.0
	 */
	public static IWorkingCopy[] getSharedWorkingCopies() {
		return JavaCore.getSharedWorkingCopies(getBufferFactory());
	}
	
	/**
	 * Returns the BufferFactory for the Java UI plug-in.
	 *
	 * @return the BufferFactory for the Java UI plug-in
	 * 
	 * @see org.eclipse.jdt.core.IBufferFactory
	 * @since 2.0
	 */
	public static IBufferFactory getBufferFactory() {
		CompilationUnitDocumentProvider provider= JavaPlugin.getDefault().getCompilationUnitDocumentProvider();
		if (provider != null)
			return provider.getBufferFactory();
		return null;
	}
	/**
	 * Returns the DocumentProvider used for Java compilation units.
	 *
	 * @return the DocumentProvider for Java compilation units.
	 * 
	 * @see IDocumentProvider
	 * @since 2.0
	 */