Bug 18132 New wizards should verify if folder is on classpath
1. create J project 'P' with source folder setup (source folder 'src') 2. use new wizard to create a class ==> you can create a class inside 'P' or in a folder which is not on the classpath
org.eclipse.jdt.ui/ui/org/eclipse/jdt/ui/wizards/NewContainerWizardPage.java
protected IStatus fContainerStatus;
	private StringButtonDialogField fContainerDialogField;
		
	/*
	 * package fragment root corresponding to the input type (can be null)
	 */
	private IPackageFragmentRoot fCurrRoot;
	
	private IWorkspaceRoot fWorkspaceRoot;
	
	public NewContainerWizardPage(String name) {
		super(name);
		fWorkspaceRoot= ResourcesPlugin.getWorkspace().getRoot();	
		ContainerFieldAdapter adapter= new ContainerFieldAdapter();
		
		fContainerDialogField= new StringButtonDialogField(adapter);
		fContainerDialogField.setDialogFieldListener(adapter);
		fContainerDialogField.setLabelText(NewWizardMessages.getString("NewContainerWizardPage.container.label")); 
		fContainerDialogField.setButtonLabel(NewWizardMessages.getString("NewContainerWizardPage.container.button")); 
		
		fContainerStatus= new StatusInfo();
		fCurrRoot= null;
	}
			
	/**
	 * Initializes the fields provided by the container page with a given
	 * Java element as selection.
	 * @param elem The initial selection of this page or null if no
	 *             selection was available
	 */